🚨 Support updating template processors (#1652)

* current updates

* simplify

* set_item works, but `tokenizer._tokenizer.post_processor[1].single = ["$0", "</s>"]` does not !

* fix: `normalizers` deserialization and other refactoring

* fix: `pre_tokenizer` deserialization

* feat: add `__len__` implementation for `normalizer::PySequence`

* feat: add `__setitem__` impl for `normalizers::PySequence`

* feat: add `__setitem__` impl to `pre_tokenizer::PySequence`

* feat: add `__setitem__` impl to `post_processor::PySequence`

* test: add normalizer sequence setter check

* refactor: allow unused `processors::setter` macro

* test: add `__setitem__` test for processors & pretok

* refactor: `unwrap` -> `PyException::new_err()?`

* refactor: fmt

* refactor: remove unnecessary `pub`

* feat(bindings): add missing getters & setters for pretoks

* feat(bindings): add missing getters & setters for processors

* refactor(bindings): rewrite RwLock poison error msg

* refactor: remove debug print

* feat(bindings): add description as to why custom deser is needed

* feat: make post proc sequence elements mutable

* fix(binding): serialization

---------

Co-authored-by: Luc Georges <luc.sydney.georges@gmail.com>

.github/workflows/python.yml

@@ -55,7 +55,6 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
-        
 
       - name: Install Rust
         uses: actions-rs/toolchain@v1

bindings/python/Cargo.toml

@@ -14,7 +14,7 @@ serde = { version = "1.0", features = ["rc", "derive"] }
 serde_json = "1.0"
 libc = "0.2"
 env_logger = "0.11"
-pyo3 = { version = "0.23", features = ["abi3", "abi3-py39"] }
+pyo3 = { version = "0.23", features = ["abi3", "abi3-py39", "py-clone"] }
 numpy = "0.23"
 ndarray = "0.16"
 itertools = "0.12"

bindings/python/pyproject.toml

@@ -2,8 +2,8 @@
 name = 'tokenizers'
 requires-python = '>=3.9'
 authors = [
-    {name = 'Nicolas Patry', email = 'patry.nicolas@protonmail.com'},
-    {name = 'Anthony Moi', email = 'anthony@huggingface.co'}
+  { name = 'Nicolas Patry', email = 'patry.nicolas@protonmail.com' },
+  { name = 'Anthony Moi', email = 'anthony@huggingface.co' },
 ]
 classifiers = [
   "Development Status :: 5 - Production/Stable",
@@ -21,12 +21,7 @@ classifiers = [
   "Topic :: Scientific/Engineering :: Artificial Intelligence",
 ]
 keywords = ["NLP", "tokenizer", "BPE", "transformer", "deep learning"]
-dynamic = [
-    'description',
-    'license',
-    'readme',
-    'version',
-]
+dynamic = ['description', 'license', 'readme', 'version']
 dependencies = ["huggingface_hub>=0.16.4,<1.0"]
 
 [project.urls]
@@ -58,16 +53,16 @@ target-version = ['py35']
 line-length = 119
 target-version = "py311"
 lint.ignore = [
-    # a == None in tests vs is None.
-    "E711",
-    # a == False in tests vs is False.
-    "E712",
-    # try.. import except.. pattern without using the lib.
-    "F401",
-    # Raw type equality is required in asserts
-    "E721",
-    # Import order
-    "E402",
-    # Fixtures unused import
-    "F811",
+  # a == None in tests vs is None.
+  "E711",
+  # a == False in tests vs is False.
+  "E712",
+  # try.. import except.. pattern without using the lib.
+  "F401",
+  # Raw type equality is required in asserts
+  "E721",
+  # Import order
+  "E402",
+  # Fixtures unused import
+  "F811",
 ]

bindings/python/src/normalizers.rs

@@ -1,3 +1,4 @@
+use pyo3::exceptions::PyException;
 use pyo3::types::*;
 use pyo3::{exceptions, prelude::*};
 use std::sync::{Arc, RwLock};
@@ -41,7 +42,7 @@ impl PyNormalizedStringMut<'_> {
 /// This class is not supposed to be instantiated directly. Instead, any implementation of a
 /// Normalizer will return an instance of this class when instantiated.
 #[pyclass(dict, module = "tokenizers.normalizers", name = "Normalizer", subclass)]
-#[derive(Clone, Serialize, Deserialize)]
+#[derive(Clone, Debug, Serialize, Deserialize)]
 #[serde(transparent)]
 pub struct PyNormalizer {
     pub(crate) normalizer: PyNormalizerTypeWrapper,
@@ -58,7 +59,11 @@ impl PyNormalizer {
                 .into_pyobject(py)?
                 .into_any()
                 .into(),
-            PyNormalizerTypeWrapper::Single(ref inner) => match &*inner.as_ref().read().unwrap() {
+            PyNormalizerTypeWrapper::Single(ref inner) => match &*inner
+                .as_ref()
+                .read()
+                .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyNormalizer"))?
+            {
                 PyNormalizerWrapper::Custom(_) => {
                     Py::new(py, base)?.into_pyobject(py)?.into_any().into()
                 }
@@ -218,7 +223,9 @@ macro_rules! getter {
     ($self: ident, $variant: ident, $name: ident) => {{
         let super_ = $self.as_ref();
         if let PyNormalizerTypeWrapper::Single(ref norm) = super_.normalizer {
-            let wrapper = norm.read().unwrap();
+            let wrapper = norm.read().expect(
+                "RwLock synchronisation primitive is poisoned, cannot get subtype of PyNormalizer",
+            );
             if let PyNormalizerWrapper::Wrapped(NormalizerWrapper::$variant(o)) = (&*wrapper) {
                 o.$name.clone()
             } else {
@@ -234,7 +241,9 @@ macro_rules! setter {
     ($self: ident, $variant: ident, $name: ident, $value: expr) => {{
         let super_ = $self.as_ref();
         if let PyNormalizerTypeWrapper::Single(ref norm) = super_.normalizer {
-            let mut wrapper = norm.write().unwrap();
+            let mut wrapper = norm.write().expect(
+                "RwLock synchronisation primitive is poisoned, cannot get subtype of PyNormalizer",
+            );
             if let PyNormalizerWrapper::Wrapped(NormalizerWrapper::$variant(ref mut o)) = *wrapper {
                 o.$name = $value;
             }
@@ -410,25 +419,55 @@ impl PySequence {
         PyTuple::new(py, [PyList::empty(py)])
     }
 
-    fn __len__(&self) -> usize {
-        0
+    fn __len__(self_: PyRef<'_, Self>) -> usize {
+        match &self_.as_ref().normalizer {
+            PyNormalizerTypeWrapper::Sequence(inner) => inner.len(),
+            PyNormalizerTypeWrapper::Single(_) => 1,
+        }
     }
 
     fn __getitem__(self_: PyRef<'_, Self>, py: Python<'_>, index: usize) -> PyResult<Py<PyAny>> {
         match &self_.as_ref().normalizer {
             PyNormalizerTypeWrapper::Sequence(inner) => match inner.get(index) {
-                Some(item) => PyNormalizer::new(PyNormalizerTypeWrapper::Single(Arc::clone(item)))
+                Some(item) => PyNormalizer::new(PyNormalizerTypeWrapper::Single(item.clone()))
                     .get_as_subtype(py),
                 _ => Err(PyErr::new::<pyo3::exceptions::PyIndexError, _>(
                     "Index not found",
                 )),
             },
             PyNormalizerTypeWrapper::Single(inner) => {
-                PyNormalizer::new(PyNormalizerTypeWrapper::Single(Arc::clone(inner)))
-                    .get_as_subtype(py)
+                PyNormalizer::new(PyNormalizerTypeWrapper::Single(inner.clone())).get_as_subtype(py)
             }
         }
     }
+
+    fn __setitem__(self_: PyRef<'_, Self>, index: usize, value: Bound<'_, PyAny>) -> PyResult<()> {
+        let norm: PyNormalizer = value.extract()?;
+        let PyNormalizerTypeWrapper::Single(norm) = norm.normalizer else {
+            return Err(PyException::new_err("normalizer should not be a sequence"));
+        };
+        match &self_.as_ref().normalizer {
+            PyNormalizerTypeWrapper::Sequence(inner) => match inner.get(index) {
+                Some(item) => {
+                    *item
+                        .write()
+                        .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyNormalizer"))? = norm
+                        .read()
+                        .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyNormalizer"))?
+                        .clone();
+                }
+                _ => {
+                    return Err(PyErr::new::<pyo3::exceptions::PyIndexError, _>(
+                        "Index not found",
+                    ))
+                }
+            },
+            PyNormalizerTypeWrapper::Single(_) => {
+                return Err(PyException::new_err("normalizer is not a sequence"))
+            }
+        };
+        Ok(())
+    }
 }
 
 /// Lowercase Normalizer
@@ -570,9 +609,31 @@ impl PyReplace {
             ToPyResult(Replace::new(pattern, content)).into_py()?.into(),
         ))
     }
+
+    #[getter]
+    fn get_pattern(_self: PyRef<Self>) -> PyResult<()> {
+        Err(PyException::new_err("Cannot get pattern"))
+    }
+
+    #[setter]
+    fn set_pattern(_self: PyRef<Self>, _pattern: PyPattern) -> PyResult<()> {
+        Err(PyException::new_err(
+            "Cannot set pattern, please instantiate a new replace pattern instead",
+        ))
+    }
+
+    #[getter]
+    fn get_content(self_: PyRef<Self>) -> String {
+        getter!(self_, Replace, content)
+    }
+
+    #[setter]
+    fn set_content(self_: PyRef<Self>, content: String) {
+        setter!(self_, Replace, content, content)
+    }
 }
 
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub(crate) struct CustomNormalizer {
     inner: PyObject,
 }
@@ -615,7 +676,7 @@ impl<'de> Deserialize<'de> for CustomNormalizer {
     }
 }
 
-#[derive(Debug, Deserialize)]
+#[derive(Clone, Debug, Deserialize)]
 #[serde(untagged)]
 pub(crate) enum PyNormalizerWrapper {
     Custom(CustomNormalizer),
@@ -634,13 +695,27 @@ impl Serialize for PyNormalizerWrapper {
     }
 }
 
-#[derive(Debug, Clone, Deserialize)]
-#[serde(untagged)]
+#[derive(Debug, Clone)]
 pub(crate) enum PyNormalizerTypeWrapper {
     Sequence(Vec<Arc<RwLock<PyNormalizerWrapper>>>),
     Single(Arc<RwLock<PyNormalizerWrapper>>),
 }
 
+/// XXX: we need to manually implement deserialize here because of the structure of the
+/// PyNormalizerTypeWrapper enum. Given the underlying PyNormalizerWrapper can contain a Sequence,
+/// default deserialization will give us a PyNormalizerTypeWrapper::Single(Sequence) when we'd like
+/// it to be PyNormalizerTypeWrapper::Sequence(// ...).
+impl<'de> Deserialize<'de> for PyNormalizerTypeWrapper {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let wrapper = NormalizerWrapper::deserialize(deserializer)?;
+        let py_wrapper: PyNormalizerWrapper = wrapper.into();
+        Ok(py_wrapper.into())
+    }
+}
+
 impl Serialize for PyNormalizerTypeWrapper {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where
@@ -672,7 +747,17 @@ where
     I: Into<PyNormalizerWrapper>,
 {
     fn from(norm: I) -> Self {
-        PyNormalizerTypeWrapper::Single(Arc::new(RwLock::new(norm.into())))
+        let norm = norm.into();
+        match norm {
+            PyNormalizerWrapper::Wrapped(NormalizerWrapper::Sequence(seq)) => {
+                PyNormalizerTypeWrapper::Sequence(
+                    seq.into_iter()
+                        .map(|e| Arc::new(RwLock::new(PyNormalizerWrapper::Wrapped(e.clone()))))
+                        .collect(),
+                )
+            }
+            _ => PyNormalizerTypeWrapper::Single(Arc::new(RwLock::new(norm))),
+        }
     }
 }
 
@@ -690,10 +775,15 @@ where
 impl Normalizer for PyNormalizerTypeWrapper {
     fn normalize(&self, normalized: &mut NormalizedString) -> tk::Result<()> {
         match self {
-            PyNormalizerTypeWrapper::Single(inner) => inner.read().unwrap().normalize(normalized),
-            PyNormalizerTypeWrapper::Sequence(inner) => inner
-                .iter()
-                .try_for_each(|n| n.read().unwrap().normalize(normalized)),
+            PyNormalizerTypeWrapper::Single(inner) => inner
+                .read()
+                .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyNormalizer"))?
+                .normalize(normalized),
+            PyNormalizerTypeWrapper::Sequence(inner) => inner.iter().try_for_each(|n| {
+                n.read()
+                    .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyNormalizer"))?
+                    .normalize(normalized)
+            }),
         }
     }
 }
@@ -793,18 +883,14 @@ mod test {
         let normalizer: PyNormalizer = serde_json::from_str(&sequence_string).unwrap();
 
         match normalizer.normalizer {
-            PyNormalizerTypeWrapper::Single(inner) => match &*inner.as_ref().read().unwrap() {
-                PyNormalizerWrapper::Wrapped(NormalizerWrapper::Sequence(sequence)) => {
-                    let normalizers = sequence.get_normalizers();
-                    assert_eq!(normalizers.len(), 1);
-                    match normalizers[0] {
-                        NormalizerWrapper::NFKC(_) => {}
-                        _ => panic!("Expected NFKC"),
-                    }
-                }
-                _ => panic!("Expected sequence"),
-            },
-            _ => panic!("Expected single"),
+            PyNormalizerTypeWrapper::Sequence(inner) => {
+                assert_eq!(inner.len(), 1);
+                match *inner[0].as_ref().read().unwrap() {
+                    PyNormalizerWrapper::Wrapped(NormalizerWrapper::NFKC(_)) => {}
+                    _ => panic!("Expected NFKC"),
+                };
+            }
+            _ => panic!("Expected sequence"),
         };
     }
 }

bindings/python/src/pre_tokenizers.rs

@@ -1,6 +1,7 @@
 use std::sync::{Arc, RwLock};
 
 use pyo3::exceptions;
+use pyo3::exceptions::PyException;
 use pyo3::prelude::*;
 use pyo3::types::*;
 use serde::ser::SerializeStruct;
@@ -48,13 +49,17 @@ impl PyPreTokenizer {
 
     pub(crate) fn get_as_subtype(&self, py: Python<'_>) -> PyResult<PyObject> {
         let base = self.clone();
-        Ok(match &self.pretok {
+        Ok(match self.pretok {
             PyPreTokenizerTypeWrapper::Sequence(_) => Py::new(py, (PySequence {}, base))?
                 .into_pyobject(py)?
                 .into_any()
                 .into(),
             PyPreTokenizerTypeWrapper::Single(ref inner) => {
-                match &*inner.as_ref().read().unwrap() {
+                match &*inner
+                    .as_ref()
+                    .read()
+                    .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPreTokenizer"))?
+                {
                     PyPreTokenizerWrapper::Custom(_) => {
                         Py::new(py, base)?.into_pyobject(py)?.into_any().into()
                     }
@@ -222,7 +227,7 @@ macro_rules! getter {
         let super_ = $self.as_ref();
         if let PyPreTokenizerTypeWrapper::Single(ref single) = super_.pretok {
             if let PyPreTokenizerWrapper::Wrapped(PreTokenizerWrapper::$variant(ref pretok)) =
-                *single.read().unwrap() {
+                *single.read().expect("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPreTokenizer") {
                     pretok.$($name)+
                 } else {
                     unreachable!()
@@ -238,7 +243,7 @@ macro_rules! setter {
         let super_ = $self.as_ref();
         if let PyPreTokenizerTypeWrapper::Single(ref single) = super_.pretok {
             if let PyPreTokenizerWrapper::Wrapped(PreTokenizerWrapper::$variant(ref mut pretok)) =
-                *single.write().unwrap()
+                *single.write().expect("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPreTokenizer")
             {
                 pretok.$name = $value;
             }
@@ -248,7 +253,7 @@ macro_rules! setter {
         let super_ = $self.as_ref();
         if let PyPreTokenizerTypeWrapper::Single(ref single) = super_.pretok {
             if let PyPreTokenizerWrapper::Wrapped(PreTokenizerWrapper::$variant(ref mut pretok)) =
-                *single.write().unwrap()
+                *single.write().expect("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPreTokenizer")
             {
                 pretok.$name($value);
             }
@@ -292,6 +297,16 @@ impl PyByteLevel {
         setter!(self_, ByteLevel, use_regex, use_regex);
     }
 
+    #[getter]
+    fn get_trim_offsets(self_: PyRef<Self>) -> bool {
+        getter!(self_, ByteLevel, trim_offsets)
+    }
+
+    #[setter]
+    fn set_trim_offsets(self_: PyRef<Self>, trim_offsets: bool) {
+        setter!(self_, ByteLevel, trim_offsets, trim_offsets)
+    }
+
     #[new]
     #[pyo3(signature = (add_prefix_space = true, use_regex = true, **_kwargs), text_signature = "(self, add_prefix_space=True, use_regex=True)")]
     fn new(
@@ -392,6 +407,52 @@ impl PySplit {
     fn __getnewargs__<'p>(&self, py: Python<'p>) -> PyResult<Bound<'p, PyTuple>> {
         PyTuple::new(py, [" ", "removed"])
     }
+
+    #[getter]
+    fn get_pattern(_self: PyRef<Self>) -> PyResult<()> {
+        Err(PyException::new_err("Cannot get pattern"))
+    }
+
+    #[setter]
+    fn set_pattern(_self: PyRef<Self>, _pattern: PyPattern) -> PyResult<()> {
+        Err(PyException::new_err(
+            "Cannot set pattern, please instantiate a new split pattern instead",
+        ))
+    }
+
+    #[getter]
+    fn get_behavior(self_: PyRef<Self>) -> String {
+        getter!(self_, Split, behavior).to_string().to_lowercase()
+    }
+
+    #[setter]
+    fn set_behavior(self_: PyRef<Self>, behavior: String) -> PyResult<()> {
+        let behavior = match behavior.as_ref() {
+            "removed" => SplitDelimiterBehavior::Removed,
+            "isolated" => SplitDelimiterBehavior::Isolated,
+            "merged_with_previous" => SplitDelimiterBehavior::MergedWithPrevious,
+            "merged_with_next" => SplitDelimiterBehavior::MergedWithNext,
+            "contiguous" => SplitDelimiterBehavior::Contiguous,
+            _ => {
+                return Err(exceptions::PyValueError::new_err(
+                    "Wrong value for SplitDelimiterBehavior, expected one of: \
+                `removed, isolated, merged_with_previous, merged_with_next, contiguous`",
+                ))
+            }
+        };
+        setter!(self_, Split, behavior, behavior);
+        Ok(())
+    }
+
+    #[getter]
+    fn get_invert(self_: PyRef<Self>) -> bool {
+        getter!(self_, Split, invert)
+    }
+
+    #[setter]
+    fn set_invert(self_: PyRef<Self>, invert: bool) {
+        setter!(self_, Split, invert, invert)
+    }
 }
 
 /// This pre-tokenizer simply splits on the provided char. Works like `.split(delimiter)`
@@ -458,6 +519,32 @@ impl PyPunctuation {
     fn new(behavior: PySplitDelimiterBehavior) -> (Self, PyPreTokenizer) {
         (PyPunctuation {}, Punctuation::new(behavior.into()).into())
     }
+
+    #[getter]
+    fn get_behavior(self_: PyRef<Self>) -> String {
+        getter!(self_, Punctuation, behavior)
+            .to_string()
+            .to_lowercase()
+    }
+
+    #[setter]
+    fn set_behavior(self_: PyRef<Self>, behavior: String) -> PyResult<()> {
+        let behavior = match behavior.as_ref() {
+            "removed" => SplitDelimiterBehavior::Removed,
+            "isolated" => SplitDelimiterBehavior::Isolated,
+            "merged_with_previous" => SplitDelimiterBehavior::MergedWithPrevious,
+            "merged_with_next" => SplitDelimiterBehavior::MergedWithNext,
+            "contiguous" => SplitDelimiterBehavior::Contiguous,
+            _ => {
+                return Err(exceptions::PyValueError::new_err(
+                    "Wrong value for SplitDelimiterBehavior, expected one of: \
+                `removed, isolated, merged_with_previous, merged_with_next, contiguous`",
+                ))
+            }
+        };
+        setter!(self_, Punctuation, behavior, behavior);
+        Ok(())
+    }
 }
 
 /// This pre-tokenizer composes other pre_tokenizers and applies them in sequence
@@ -491,20 +578,47 @@ impl PySequence {
     fn __getitem__(self_: PyRef<'_, Self>, py: Python<'_>, index: usize) -> PyResult<Py<PyAny>> {
         match &self_.as_ref().pretok {
             PyPreTokenizerTypeWrapper::Sequence(inner) => match inner.get(index) {
-                Some(item) => {
-                    PyPreTokenizer::new(PyPreTokenizerTypeWrapper::Single(Arc::clone(item)))
-                        .get_as_subtype(py)
-                }
+                Some(item) => PyPreTokenizer::new(PyPreTokenizerTypeWrapper::Single(item.clone()))
+                    .get_as_subtype(py),
                 _ => Err(PyErr::new::<pyo3::exceptions::PyIndexError, _>(
                     "Index not found",
                 )),
             },
-            PyPreTokenizerTypeWrapper::Single(inner) => {
-                PyPreTokenizer::new(PyPreTokenizerTypeWrapper::Single(Arc::clone(inner)))
-                    .get_as_subtype(py)
-            }
+            _ => Err(PyErr::new::<pyo3::exceptions::PyIndexError, _>(
+                "This processor is not a Sequence, it does not support __getitem__",
+            )),
         }
     }
+
+    fn __setitem__(self_: PyRef<'_, Self>, index: usize, value: Bound<'_, PyAny>) -> PyResult<()> {
+        let pretok: PyPreTokenizer = value.extract()?;
+        let PyPreTokenizerTypeWrapper::Single(pretok) = pretok.pretok else {
+            return Err(PyException::new_err(
+                "pre tokenizer should not be a sequence",
+            ));
+        };
+        match &self_.as_ref().pretok {
+            PyPreTokenizerTypeWrapper::Sequence(inner) => match inner.get(index) {
+                Some(item) => {
+                    *item
+                        .write()
+                        .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPreTokenizer"))? = (*pretok
+                        .read()
+                        .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPreTokenizer"))?)
+                    .clone();
+                }
+                _ => {
+                    return Err(PyErr::new::<pyo3::exceptions::PyIndexError, _>(
+                        "Index not found",
+                    ))
+                }
+            },
+            PyPreTokenizerTypeWrapper::Single(_) => {
+                return Err(PyException::new_err("pre tokenizer is not a sequence"))
+            }
+        };
+        Ok(())
+    }
 }
 
 pub(crate) fn from_string(string: String) -> Result<PrependScheme, PyErr> {
@@ -565,13 +679,7 @@ impl PyMetaspace {
     #[getter]
     fn get_prepend_scheme(self_: PyRef<Self>) -> String {
         // Assuming Metaspace has a method to get the prepend_scheme as a string
-        let scheme: PrependScheme = getter!(self_, Metaspace, get_prepend_scheme());
-        match scheme {
-            PrependScheme::First => "first",
-            PrependScheme::Never => "never",
-            PrependScheme::Always => "always",
-        }
-        .to_string()
+        getter!(self_, Metaspace, get_prepend_scheme()).to_string()
     }
 
     #[setter]
@@ -642,6 +750,7 @@ impl PyUnicodeScripts {
     }
 }
 
+#[derive(Clone)]
 pub(crate) struct CustomPreTokenizer {
     inner: PyObject,
 }
@@ -685,7 +794,7 @@ impl<'de> Deserialize<'de> for CustomPreTokenizer {
     }
 }
 
-#[derive(Deserialize)]
+#[derive(Clone, Deserialize)]
 #[serde(untagged)]
 pub(crate) enum PyPreTokenizerWrapper {
     Custom(CustomPreTokenizer),
@@ -704,13 +813,23 @@ impl Serialize for PyPreTokenizerWrapper {
     }
 }
 
-#[derive(Clone, Deserialize)]
-#[serde(untagged)]
+#[derive(Clone)]
 pub(crate) enum PyPreTokenizerTypeWrapper {
     Sequence(Vec<Arc<RwLock<PyPreTokenizerWrapper>>>),
     Single(Arc<RwLock<PyPreTokenizerWrapper>>),
 }
 
+impl<'de> Deserialize<'de> for PyPreTokenizerTypeWrapper {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let wrapper = PreTokenizerWrapper::deserialize(deserializer)?;
+        let py_wrapper: PyPreTokenizerWrapper = wrapper.into();
+        Ok(py_wrapper.into())
+    }
+}
+
 impl Serialize for PyPreTokenizerTypeWrapper {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where
@@ -742,7 +861,17 @@ where
     I: Into<PyPreTokenizerWrapper>,
 {
     fn from(pretok: I) -> Self {
-        PyPreTokenizerTypeWrapper::Single(Arc::new(RwLock::new(pretok.into())))
+        let pretok = pretok.into();
+        match pretok {
+            PyPreTokenizerWrapper::Wrapped(PreTokenizerWrapper::Sequence(seq)) => {
+                PyPreTokenizerTypeWrapper::Sequence(
+                    seq.into_iter()
+                        .map(|e| Arc::new(RwLock::new(PyPreTokenizerWrapper::Wrapped(e.clone()))))
+                        .collect(),
+                )
+            }
+            _ => PyPreTokenizerTypeWrapper::Single(Arc::new(RwLock::new(pretok))),
+        }
     }
 }
 
@@ -760,10 +889,15 @@ where
 impl PreTokenizer for PyPreTokenizerTypeWrapper {
     fn pre_tokenize(&self, pretok: &mut PreTokenizedString) -> tk::Result<()> {
         match self {
-            PyPreTokenizerTypeWrapper::Single(inner) => inner.read().unwrap().pre_tokenize(pretok),
-            PyPreTokenizerTypeWrapper::Sequence(inner) => inner
-                .iter()
-                .try_for_each(|n| n.read().unwrap().pre_tokenize(pretok)),
+            PyPreTokenizerTypeWrapper::Single(inner) => inner
+                .read()
+                .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPreTokenizer"))?
+                .pre_tokenize(pretok),
+            PyPreTokenizerTypeWrapper::Sequence(inner) => inner.iter().try_for_each(|n| {
+                n.read()
+                    .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPreTokenizer"))?
+                    .pre_tokenize(pretok)
+            }),
         }
     }
 }

bindings/python/src/processors.rs

@@ -1,17 +1,20 @@
 use std::convert::TryInto;
 use std::sync::Arc;
-
-use pyo3::exceptions;
-use pyo3::prelude::*;
-use pyo3::types::*;
+use std::sync::RwLock;
 
 use crate::encoding::PyEncoding;
 use crate::error::ToPyResult;
+use pyo3::exceptions;
+use pyo3::exceptions::PyException;
+use pyo3::prelude::*;
+use pyo3::types::*;
+use serde::ser::SerializeStruct;
+use serde::Deserializer;
+use serde::Serializer;
 use serde::{Deserialize, Serialize};
 use tk::processors::bert::BertProcessing;
 use tk::processors::byte_level::ByteLevel;
 use tk::processors::roberta::RobertaProcessing;
-use tk::processors::sequence::Sequence;
 use tk::processors::template::{SpecialToken, Template};
 use tk::processors::PostProcessorWrapper;
 use tk::{Encoding, PostProcessor};
@@ -30,42 +33,67 @@ use tokenizers as tk;
 #[derive(Clone, Deserialize, Serialize)]
 #[serde(transparent)]
 pub struct PyPostProcessor {
-    pub processor: Arc<PostProcessorWrapper>,
+    processor: PyPostProcessorTypeWrapper,
+}
+
+impl<I> From<I> for PyPostProcessor
+where
+    I: Into<PostProcessorWrapper>,
+{
+    fn from(processor: I) -> Self {
+        PyPostProcessor {
+            processor: processor.into().into(),
+        }
+    }
 }
 
 impl PyPostProcessor {
-    pub fn new(processor: Arc<PostProcessorWrapper>) -> Self {
+    pub(crate) fn new(processor: PyPostProcessorTypeWrapper) -> Self {
         PyPostProcessor { processor }
     }
 
     pub(crate) fn get_as_subtype(&self, py: Python<'_>) -> PyResult<PyObject> {
         let base = self.clone();
-        Ok(match self.processor.as_ref() {
-            PostProcessorWrapper::ByteLevel(_) => Py::new(py, (PyByteLevel {}, base))?
+        Ok(
+            match self.processor {
+                PyPostProcessorTypeWrapper::Sequence(_) => Py::new(py, (PySequence {}, base))?
                 .into_pyobject(py)?
                 .into_any()
                 .into(),
-            PostProcessorWrapper::Bert(_) => Py::new(py, (PyBertProcessing {}, base))?
-                .into_pyobject(py)?
-                .into_any()
-                .into(),
-            PostProcessorWrapper::Roberta(_) => Py::new(py, (PyRobertaProcessing {}, base))?
-                .into_pyobject(py)?
-                .into_any()
-                .into(),
-            PostProcessorWrapper::Template(_) => Py::new(py, (PyTemplateProcessing {}, base))?
-                .into_pyobject(py)?
-                .into_any()
-                .into(),
-            PostProcessorWrapper::Sequence(_) => Py::new(py, (PySequence {}, base))?
-                .into_pyobject(py)?
-                .into_any()
-                .into(),
-        })
+                PyPostProcessorTypeWrapper::Single(ref inner) => {
+
+            match &*inner.read().map_err(|_| {
+                PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPostProcessor")
+            })? {
+                PostProcessorWrapper::ByteLevel(_) => Py::new(py, (PyByteLevel {}, base))?
+                    .into_pyobject(py)?
+                    .into_any()
+                    .into(),
+                PostProcessorWrapper::Bert(_) => Py::new(py, (PyBertProcessing {}, base))?
+                    .into_pyobject(py)?
+                    .into_any()
+                    .into(),
+                PostProcessorWrapper::Roberta(_) => Py::new(py, (PyRobertaProcessing {}, base))?
+                    .into_pyobject(py)?
+                    .into_any()
+                    .into(),
+                PostProcessorWrapper::Template(_) => Py::new(py, (PyTemplateProcessing {}, base))?
+                    .into_pyobject(py)?
+                    .into_any()
+                    .into(),
+                PostProcessorWrapper::Sequence(_) => Py::new(py, (PySequence {}, base))?
+                    .into_pyobject(py)?
+                    .into_any()
+                    .into(),
+            }
+                }
+            }
+        )
     }
 }
 
 impl PostProcessor for PyPostProcessor {
+    // TODO: update signature to `tk::Result<usize>`
     fn added_tokens(&self, is_pair: bool) -> usize {
         self.processor.added_tokens(is_pair)
     }
@@ -83,7 +111,7 @@ impl PostProcessor for PyPostProcessor {
 #[pymethods]
 impl PyPostProcessor {
     fn __getstate__(&self, py: Python) -> PyResult<PyObject> {
-        let data = serde_json::to_string(self.processor.as_ref()).map_err(|e| {
+        let data = serde_json::to_string(&self.processor).map_err(|e| {
             exceptions::PyException::new_err(format!(
                 "Error while attempting to pickle PostProcessor: {}",
                 e
@@ -116,8 +144,8 @@ impl PyPostProcessor {
     /// Returns:
     ///     :obj:`int`: The number of tokens to add
     #[pyo3(text_signature = "(self, is_pair)")]
-    fn num_special_tokens_to_add(&self, is_pair: bool) -> usize {
-        self.processor.added_tokens(is_pair)
+    fn num_special_tokens_to_add(&self, is_pair: bool) -> PyResult<usize> {
+        Ok(self.processor.added_tokens(is_pair))
     }
 
     /// Post-process the given encodings, generating the final one
@@ -162,6 +190,132 @@ impl PyPostProcessor {
     }
 }
 
+macro_rules! getter {
+    ($self: ident, $variant: ident, $($name: tt)+) => {{
+        let super_ = $self.as_ref();
+        if let PyPostProcessorTypeWrapper::Single(ref single) = super_.processor {
+            if let PostProcessorWrapper::$variant(ref post) = *single.read().expect(
+                "RwLock synchronisation primitive is poisoned, cannot get subtype of PyPostProcessor"
+            ) {
+                post.$($name)+
+            } else {
+                unreachable!()
+            }
+        } else {
+            unreachable!()
+        }
+    }};
+}
+
+macro_rules! setter {
+    ($self: ident, $variant: ident, $name: ident, $value: expr) => {{
+        let super_ = $self.as_ref();
+        if let PyPostProcessorTypeWrapper::Single(ref single) = super_.processor {
+        if let PostProcessorWrapper::$variant(ref mut post) = *single.write().expect(
+            "RwLock synchronisation primitive is poisoned, cannot get subtype of PyPostProcessor",
+        ) {
+            post.$name = $value;
+        }
+        }
+    }};
+    ($self: ident, $variant: ident, @$name: ident, $value: expr) => {{
+        let super_ = $self.as_ref();
+        if let PyPostProcessorTypeWrapper::Single(ref single) = super_.processor {
+        if let PostProcessorWrapper::$variant(ref mut post) = *single.write().expect(
+            "RwLock synchronisation primitive is poisoned, cannot get subtype of PyPostProcessor",
+        ) {
+            post.$name($value);
+        }
+        }
+    };};
+}
+
+#[derive(Clone)]
+pub(crate) enum PyPostProcessorTypeWrapper {
+    Sequence(Vec<Arc<RwLock<PostProcessorWrapper>>>),
+    Single(Arc<RwLock<PostProcessorWrapper>>),
+}
+
+impl PostProcessor for PyPostProcessorTypeWrapper {
+    fn added_tokens(&self, is_pair: bool) -> usize {
+        match self {
+            PyPostProcessorTypeWrapper::Single(inner) => inner
+                .read()
+                .expect("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPostProcessor")
+                .added_tokens(is_pair),
+            PyPostProcessorTypeWrapper::Sequence(inner) => inner.iter().map(|p| {
+                p.read()
+                    .expect("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPostProcessor")
+                    .added_tokens(is_pair)
+            }).sum::<usize>(),
+        }
+    }
+
+    fn process_encodings(
+        &self,
+        mut encodings: Vec<Encoding>,
+        add_special_tokens: bool,
+    ) -> tk::Result<Vec<Encoding>> {
+        match self {
+            PyPostProcessorTypeWrapper::Single(inner) => inner
+                .read()
+                .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPreTokenizer"))?
+                .process_encodings(encodings, add_special_tokens),
+            PyPostProcessorTypeWrapper::Sequence(inner) => {
+                for processor in inner.iter() {
+                    encodings = processor
+                        .read()
+                        .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPreTokenizer"))?
+                        .process_encodings(encodings, add_special_tokens)?;
+                }
+        Ok(encodings)
+            },
+        }
+    }
+}
+
+impl<'de> Deserialize<'de> for PyPostProcessorTypeWrapper {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let wrapper = PostProcessorWrapper::deserialize(deserializer)?;
+        Ok(wrapper.into())
+    }
+}
+
+impl Serialize for PyPostProcessorTypeWrapper {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        match self {
+            PyPostProcessorTypeWrapper::Sequence(seq) => {
+                let mut ser = serializer.serialize_struct("Sequence", 2)?;
+                ser.serialize_field("type", "Sequence")?;
+                ser.serialize_field("processors", seq)?;
+                ser.end()
+            }
+            PyPostProcessorTypeWrapper::Single(inner) => inner.serialize(serializer),
+        }
+    }
+}
+
+impl<I> From<I> for PyPostProcessorTypeWrapper
+where
+    I: Into<PostProcessorWrapper>,
+{
+    fn from(processor: I) -> Self {
+        let processor = processor.into();
+        match processor {
+            PostProcessorWrapper::Sequence(seq) => PyPostProcessorTypeWrapper::Sequence(
+                seq.into_iter().map(|p| Arc::new(RwLock::new(p))).collect(),
+            ),
+            _ => PyPostProcessorTypeWrapper::Single(Arc::new(RwLock::new(processor.clone()))),
+        }
+    }
+}
+
 /// This post-processor takes care of adding the special tokens needed by
 /// a Bert model:
 ///
@@ -181,15 +335,46 @@ impl PyBertProcessing {
     #[new]
     #[pyo3(text_signature = "(self, sep, cls)")]
     fn new(sep: (String, u32), cls: (String, u32)) -> (Self, PyPostProcessor) {
-        (
-            PyBertProcessing {},
-            PyPostProcessor::new(Arc::new(BertProcessing::new(sep, cls).into())),
-        )
+        (PyBertProcessing {}, BertProcessing::new(sep, cls).into())
     }
 
     fn __getnewargs__<'p>(&self, py: Python<'p>) -> PyResult<Bound<'p, PyTuple>> {
         PyTuple::new(py, [("", 0), ("", 0)])
     }
+
+    #[getter]
+    fn get_sep(self_: PyRef<Self>) -> Result<Bound<'_, PyTuple>, PyErr> {
+        let py = self_.py();
+        let (tok, id) = getter!(self_, Bert, get_sep_copy());
+        PyTuple::new(
+            py,
+            Vec::<PyObject>::from([tok.into_pyobject(py)?.into(), id.into_pyobject(py)?.into()]),
+        )
+    }
+
+    #[setter]
+    fn set_sep(self_: PyRef<Self>, sep: Bound<'_, PyTuple>) -> PyResult<()> {
+        let sep = sep.extract()?;
+        setter!(self_, Bert, sep, sep);
+        Ok(())
+    }
+
+    #[getter]
+    fn get_cls(self_: PyRef<Self>) -> Result<Bound<'_, PyTuple>, PyErr> {
+        let py = self_.py();
+        let (tok, id) = getter!(self_, Bert, get_cls_copy());
+        PyTuple::new(
+            py,
+            Vec::<PyObject>::from([tok.into_pyobject(py)?.into(), id.into_pyobject(py)?.into()]),
+        )
+    }
+
+    #[setter]
+    fn set_cls(self_: PyRef<Self>, cls: Bound<'_, PyTuple>) -> PyResult<()> {
+        let cls = cls.extract()?;
+        setter!(self_, Bert, cls, cls);
+        Ok(())
+    }
 }
 
 /// This post-processor takes care of adding the special tokens needed by
@@ -231,15 +416,66 @@ impl PyRobertaProcessing {
         let proc = RobertaProcessing::new(sep, cls)
             .trim_offsets(trim_offsets)
             .add_prefix_space(add_prefix_space);
-        (
-            PyRobertaProcessing {},
-            PyPostProcessor::new(Arc::new(proc.into())),
-        )
+        (PyRobertaProcessing {}, proc.into())
     }
 
     fn __getnewargs__<'p>(&self, py: Python<'p>) -> PyResult<Bound<'p, PyTuple>> {
         PyTuple::new(py, [("", 0), ("", 0)])
     }
+
+    #[getter]
+    fn get_sep(self_: PyRef<Self>) -> Result<Bound<'_, PyTuple>, PyErr> {
+        let py = self_.py();
+        let (tok, id) = getter!(self_, Roberta, get_sep_copy());
+        PyTuple::new(
+            py,
+            Vec::<PyObject>::from([tok.into_pyobject(py)?.into(), id.into_pyobject(py)?.into()]),
+        )
+    }
+
+    #[setter]
+    fn set_sep(self_: PyRef<Self>, sep: Bound<'_, PyTuple>) -> PyResult<()> {
+        let sep = sep.extract()?;
+        setter!(self_, Roberta, sep, sep);
+        Ok(())
+    }
+
+    #[getter]
+    fn get_cls(self_: PyRef<Self>) -> Result<Bound<'_, PyTuple>, PyErr> {
+        let py = self_.py();
+        let (tok, id) = getter!(self_, Roberta, get_cls_copy());
+        PyTuple::new(
+            py,
+            Vec::<PyObject>::from([tok.into_pyobject(py)?.into(), id.into_pyobject(py)?.into()]),
+        )
+    }
+
+    #[setter]
+    fn set_cls(self_: PyRef<Self>, cls: Bound<'_, PyTuple>) -> PyResult<()> {
+        let cls = cls.extract()?;
+        setter!(self_, Roberta, cls, cls);
+        Ok(())
+    }
+
+    #[getter]
+    fn get_trim_offsets(self_: PyRef<Self>) -> bool {
+        getter!(self_, Roberta, trim_offsets)
+    }
+
+    #[setter]
+    fn set_trim_offsets(self_: PyRef<Self>, trim_offsets: bool) {
+        setter!(self_, Roberta, trim_offsets, trim_offsets)
+    }
+
+    #[getter]
+    fn get_add_prefix_space(self_: PyRef<Self>) -> bool {
+        getter!(self_, Roberta, add_prefix_space)
+    }
+
+    #[setter]
+    fn set_add_prefix_space(self_: PyRef<Self>, add_prefix_space: bool) {
+        setter!(self_, Roberta, add_prefix_space, add_prefix_space)
+    }
 }
 
 /// This post-processor takes care of trimming the offsets.
@@ -255,21 +491,58 @@ pub struct PyByteLevel {}
 #[pymethods]
 impl PyByteLevel {
     #[new]
-    #[pyo3(signature = (trim_offsets = None, **_kwargs), text_signature = "(self, trim_offsets=True)")]
+    #[pyo3(signature = (add_prefix_space = None, trim_offsets = None, use_regex = None, **_kwargs), text_signature = "(self, trim_offsets=True)")]
     fn new(
+        add_prefix_space: Option<bool>,
         trim_offsets: Option<bool>,
+        use_regex: Option<bool>,
         _kwargs: Option<&Bound<'_, PyDict>>,
     ) -> (Self, PyPostProcessor) {
         let mut byte_level = ByteLevel::default();
 
+        if let Some(aps) = add_prefix_space {
+            byte_level = byte_level.add_prefix_space(aps);
+        }
+
         if let Some(to) = trim_offsets {
             byte_level = byte_level.trim_offsets(to);
         }
 
-        (
-            PyByteLevel {},
-            PyPostProcessor::new(Arc::new(byte_level.into())),
-        )
+        if let Some(ur) = use_regex {
+            byte_level = byte_level.use_regex(ur);
+        }
+
+        (PyByteLevel {}, byte_level.into())
+    }
+
+    #[getter]
+    fn get_add_prefix_space(self_: PyRef<Self>) -> bool {
+        getter!(self_, ByteLevel, add_prefix_space)
+    }
+
+    #[setter]
+    fn set_add_prefix_space(self_: PyRef<Self>, add_prefix_space: bool) {
+        setter!(self_, ByteLevel, add_prefix_space, add_prefix_space)
+    }
+
+    #[getter]
+    fn get_trim_offsets(self_: PyRef<Self>) -> bool {
+        getter!(self_, ByteLevel, trim_offsets)
+    }
+
+    #[setter]
+    fn set_trim_offsets(self_: PyRef<Self>, trim_offsets: bool) {
+        setter!(self_, ByteLevel, trim_offsets, trim_offsets)
+    }
+
+    #[getter]
+    fn get_use_regex(self_: PyRef<Self>) -> bool {
+        getter!(self_, ByteLevel, use_regex)
+    }
+
+    #[setter]
+    fn set_use_regex(self_: PyRef<Self>, use_regex: bool) {
+        setter!(self_, ByteLevel, use_regex, use_regex)
     }
 }
 
@@ -430,10 +703,26 @@ impl PyTemplateProcessing {
             .build()
             .map_err(|e| exceptions::PyValueError::new_err(e.to_string()))?;
 
-        Ok((
-            PyTemplateProcessing {},
-            PyPostProcessor::new(Arc::new(processor.into())),
-        ))
+        Ok((PyTemplateProcessing {}, processor.into()))
+    }
+
+    #[getter]
+    fn get_single(self_: PyRef<Self>) -> String {
+        getter!(self_, Template, get_single())
+    }
+
+    #[setter]
+    fn set_single(self_: PyRef<Self>, single: PyTemplate) -> PyResult<()> {
+        let template: Template = Template::from(single);
+        let super_ = self_.as_ref();
+        if let PyPostProcessorTypeWrapper::Single(ref inner) = super_.processor {
+            if let PostProcessorWrapper::Template(ref mut post) = *inner
+                .write()
+                .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPostProcessor"))? {
+                post.set_single(template);
+            }
+        }
+        Ok(())
     }
 }
 
@@ -444,27 +733,79 @@ impl PyTemplateProcessing {
 ///         The processors that need to be chained
 #[pyclass(extends=PyPostProcessor, module = "tokenizers.processors", name = "Sequence")]
 pub struct PySequence {}
+
 #[pymethods]
 impl PySequence {
     #[new]
     #[pyo3(signature = (processors_py), text_signature = "(self, processors)")]
-    fn new(processors_py: &Bound<'_, PyList>) -> (Self, PyPostProcessor) {
-        let mut processors: Vec<PostProcessorWrapper> = Vec::with_capacity(processors_py.len());
+    fn new(processors_py: &Bound<'_, PyList>) -> PyResult<(Self, PyPostProcessor)> {
+        let mut processors = Vec::with_capacity(processors_py.len());
         for n in processors_py.iter() {
-            let processor: PyRef<PyPostProcessor> = n.extract().unwrap();
-            let processor = processor.processor.as_ref();
-            processors.push(processor.clone());
+            let processor: PyRef<PyPostProcessor> = n.extract()?;
+            match &processor.processor {
+                PyPostProcessorTypeWrapper::Sequence(inner) => {
+                    processors.extend(inner.iter().cloned())
+                }
+                PyPostProcessorTypeWrapper::Single(inner) => processors.push(inner.clone()),
+            }
         }
-        let sequence_processor = Sequence::new(processors);
-        (
+        Ok((
             PySequence {},
-            PyPostProcessor::new(Arc::new(PostProcessorWrapper::Sequence(sequence_processor))),
-        )
+            PyPostProcessor::new(PyPostProcessorTypeWrapper::Sequence(processors)),
+        ))
     }
 
     fn __getnewargs__<'p>(&self, py: Python<'p>) -> PyResult<Bound<'p, PyTuple>> {
         PyTuple::new(py, [PyList::empty(py)])
     }
+
+    fn __getitem__(self_: PyRef<'_, Self>, py: Python<'_>, index: usize) -> PyResult<Py<PyAny>> {
+        match &self_.as_ref().processor {
+            PyPostProcessorTypeWrapper::Sequence(ref inner) => match inner.get(index) {
+                Some(item) => {
+                    PyPostProcessor::new(PyPostProcessorTypeWrapper::Single(item.clone()))
+                        .get_as_subtype(py)
+                }
+                _ => Err(PyErr::new::<pyo3::exceptions::PyIndexError, _>(
+                    "Index not found",
+                )),
+            },
+            _ => Err(PyErr::new::<pyo3::exceptions::PyIndexError, _>(
+                "This processor is not a Sequence, it does not support __getitem__",
+            )),
+        }
+    }
+
+    fn __setitem__(self_: PyRef<'_, Self>, index: usize, value: Bound<'_, PyAny>) -> PyResult<()> {
+        let processor: PyPostProcessor = value.extract()?;
+        let PyPostProcessorTypeWrapper::Single(processor) = processor.processor else {
+            return Err(PyException::new_err("processor should not be a sequence"));
+        };
+
+        match &self_.as_ref().processor {
+            PyPostProcessorTypeWrapper::Sequence(inner) => match inner.get(index) {
+                Some(item) => {
+                    *item
+                        .write()
+                        .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPostProcessor"))? = processor
+                        .read()
+                        .map_err(|_| PyException::new_err("RwLock synchronisation primitive is poisoned, cannot get subtype of PyPostProcessor"))?
+                        .clone();
+                }
+                _ => {
+                    return Err(PyErr::new::<pyo3::exceptions::PyIndexError, _>(
+                        "Index not found",
+                    ))
+                }
+            },
+            _ => {
+                return Err(PyException::new_err(
+                    "This processor is not a Sequence, it does not support __setitem__",
+                ))
+            }
+        };
+        Ok(())
+    }
 }
 
 /// Processors Module
@@ -481,20 +822,20 @@ pub fn processors(m: &Bound<'_, PyModule>) -> PyResult<()> {
 
 #[cfg(test)]
 mod test {
-    use std::sync::Arc;
+    use std::sync::{Arc, RwLock};
 
     use pyo3::prelude::*;
     use tk::processors::bert::BertProcessing;
     use tk::processors::PostProcessorWrapper;
 
-    use crate::processors::PyPostProcessor;
+    use crate::processors::{PyPostProcessor, PyPostProcessorTypeWrapper};
 
     #[test]
     fn get_subtype() {
         Python::with_gil(|py| {
-            let py_proc = PyPostProcessor::new(Arc::new(
-                BertProcessing::new(("SEP".into(), 0), ("CLS".into(), 1)).into(),
-            ));
+            let py_proc = PyPostProcessor::new(PyPostProcessorTypeWrapper::Single(Arc::new(
+                RwLock::new(BertProcessing::new(("SEP".into(), 0), ("CLS".into(), 1)).into()),
+            )));
             let py_bert = py_proc.get_as_subtype(py).unwrap();
             assert_eq!(
                 "BertProcessing",
@@ -510,21 +851,29 @@ mod test {
         let rs_processing_ser = serde_json::to_string(&rs_processing).unwrap();
         let rs_wrapper_ser = serde_json::to_string(&rs_wrapper).unwrap();
 
-        let py_processing = PyPostProcessor::new(Arc::new(rs_wrapper));
+        let py_processing = PyPostProcessor::new(PyPostProcessorTypeWrapper::Single(Arc::new(
+            RwLock::new(rs_wrapper),
+        )));
         let py_ser = serde_json::to_string(&py_processing).unwrap();
         assert_eq!(py_ser, rs_processing_ser);
         assert_eq!(py_ser, rs_wrapper_ser);
 
         let py_processing: PyPostProcessor = serde_json::from_str(&rs_processing_ser).unwrap();
-        match py_processing.processor.as_ref() {
-            PostProcessorWrapper::Bert(_) => (),
-            _ => panic!("Expected Bert postprocessor."),
+        match py_processing.processor {
+            PyPostProcessorTypeWrapper::Single(inner) => match *inner.as_ref().read().unwrap() {
+                PostProcessorWrapper::Bert(_) => (),
+                _ => panic!("Expected Bert postprocessor."),
+            },
+            _ => panic!("Expected a single processor, got a sequence"),
         }
 
         let py_processing: PyPostProcessor = serde_json::from_str(&rs_wrapper_ser).unwrap();
-        match py_processing.processor.as_ref() {
-            PostProcessorWrapper::Bert(_) => (),
-            _ => panic!("Expected Bert postprocessor."),
-        }
+        match py_processing.processor {
+            PyPostProcessorTypeWrapper::Single(inner) => match *inner.as_ref().read().unwrap() {
+                PostProcessorWrapper::Bert(_) => (),
+                _ => panic!("Expected Bert postprocessor."),
+            },
+            _ => panic!("Expected a single processor, got a sequence"),
+        };
     }
 }

bindings/python/src/utils/normalization.rs

@@ -117,6 +117,12 @@ impl From<PySplitDelimiterBehavior> for SplitDelimiterBehavior {
     }
 }
 
+impl From<SplitDelimiterBehavior> for PySplitDelimiterBehavior {
+    fn from(v: SplitDelimiterBehavior) -> Self {
+        Self(v)
+    }
+}
+
 fn filter(normalized: &mut NormalizedString, func: &Bound<'_, PyAny>) -> PyResult<()> {
     let err = "`filter` expect a callable with the signature: `fn(char) -> bool`";
 

bindings/python/tests/bindings/test_normalizers.py

@@ -3,7 +3,16 @@ import pickle
 import pytest
 
 from tokenizers import NormalizedString
-from tokenizers.normalizers import BertNormalizer, Lowercase, Normalizer, Sequence, Strip, Prepend
+from tokenizers.normalizers import (
+    BertNormalizer,
+    Lowercase,
+    Normalizer,
+    Precompiled,
+    Sequence,
+    Strip,
+    Prepend,
+    Replace,
+)
 
 
 class TestBertNormalizer:
@@ -67,14 +76,57 @@ class TestSequence:
         output = normalizer.normalize_str("  HELLO  ")
         assert output == "hello"
 
-    def test_items(self):
-        normalizers = Sequence([BertNormalizer(True, True), Prepend(), Strip()])
+    def test_set_item(self):
+        normalizers = Sequence(
+            [
+                BertNormalizer(True, True),
+                Prepend(prepend="test"),
+            ]
+        )
+        assert normalizers[0].__class__ == BertNormalizer
         assert normalizers[1].__class__ == Prepend
-        normalizers[0].lowercase = False
-        assert not normalizers[0].lowercase
-        assert normalizers[2].__class__ == Strip
+        normalizers[1] = Strip()
+        assert normalizers[1].__class__ == Strip
         with pytest.raises(IndexError):
-            print(normalizers[3])
+            print(normalizers[2])
+
+    def test_item_getters_and_setters(self):
+        normalizers = Sequence(
+            [
+                BertNormalizer(clean_text=True, handle_chinese_chars=True, strip_accents=True, lowercase=True),
+                Strip(left=True, right=True),
+                Prepend(prepend="_"),
+                Replace(pattern="something", content="else"),
+            ]
+        )
+
+        assert normalizers[0].__class__ == BertNormalizer
+        normalizers[0].clean_text = False
+        normalizers[0].handle_chinese_chars = False
+        normalizers[0].strip_accents = False
+        normalizers[0].lowercase = False
+        assert not normalizers[0].clean_text
+        assert not normalizers[0].handle_chinese_chars
+        assert not normalizers[0].strip_accents
+        assert not normalizers[0].lowercase
+
+        assert normalizers[1].__class__ == Strip
+        normalizers[1].left = False
+        normalizers[1].right = False
+        assert not normalizers[1].left
+        assert not normalizers[1].right
+
+        assert normalizers[2].__class__ == Prepend
+        normalizers[2].prepend = " "
+        assert normalizers[2].prepend == " "
+
+        assert normalizers[3].__class__ == Replace
+        with pytest.raises(Exception):
+            normalizers[3].pattern = "test"
+        with pytest.raises(Exception):
+            print(normalizers[3].pattern)
+        normalizers[3].content = "test"
+        assert normalizers[3].content == "test"
 
 
 class TestLowercase:

bindings/python/tests/bindings/test_pre_tokenizers.py

@@ -169,12 +169,69 @@ class TestSequence:
             ("?", (29, 30)),
         ]
 
-    def test_items(self):
-        pre_tokenizers = Sequence([Metaspace("a", "never", split=True), Punctuation()])
-        assert pre_tokenizers[1].__class__ == Punctuation
-        assert pre_tokenizers[0].__class__ == Metaspace
-        pre_tokenizers[0].split = False
-        assert not pre_tokenizers[0].split
+    def test_set_item(self):
+        pre_tokenizers = Sequence(
+            [
+                ByteLevel(),
+                Split(pattern="/test/", behavior="removed"),
+            ]
+        )
+        assert pre_tokenizers[0].__class__ == ByteLevel
+        assert pre_tokenizers[1].__class__ == Split
+        pre_tokenizers[1] = Metaspace()
+        assert pre_tokenizers[1].__class__ == Metaspace
+        with pytest.raises(IndexError):
+            print(pre_tokenizers[2])
+
+    def test_item_getters_and_setters(self):
+        pre_tokenizers = Sequence(
+            [
+                ByteLevel(add_prefix_space=True, trim_offsets=True, use_regex=True),
+                Split(pattern="/test/", behavior="removed", invert=False),
+                Metaspace("a", "never", split=False),
+                CharDelimiterSplit(delimiter=" "),
+                Punctuation(behavior="removed"),
+                Digits(individual_digits=True),
+            ]
+        )
+
+        assert pre_tokenizers[0].__class__ == ByteLevel
+        pre_tokenizers[0].add_prefix_space = False
+        pre_tokenizers[0].trim_offsets = False
+        pre_tokenizers[0].use_regex = False
+        assert not pre_tokenizers[0].add_prefix_space
+        assert not pre_tokenizers[0].trim_offsets
+        assert not pre_tokenizers[0].use_regex
+
+        assert pre_tokenizers[1].__class__ == Split
+        with pytest.raises(Exception):
+            pre_tokenizers[1].pattern = "/pattern/"
+        pre_tokenizers[1].behavior = "isolated"
+        pre_tokenizers[1].invert = True
+        with pytest.raises(Exception):
+            pre_tokenizers[1].pattern
+        assert pre_tokenizers[1].behavior == "isolated"
+        assert pre_tokenizers[1].invert
+
+        assert pre_tokenizers[2].__class__ == Metaspace
+        pre_tokenizers[2].replacement = " "
+        pre_tokenizers[2].prepend_scheme = "always"
+        pre_tokenizers[2].split = True
+        assert pre_tokenizers[2].replacement == " "
+        assert pre_tokenizers[2].prepend_scheme == "always"
+        assert pre_tokenizers[2].split
+
+        assert pre_tokenizers[3].__class__ == CharDelimiterSplit
+        pre_tokenizers[3].delimiter = "_"
+        assert pre_tokenizers[3].delimiter == "_"
+
+        assert pre_tokenizers[4].__class__ == Punctuation
+        pre_tokenizers[4].behavior = "isolated"
+        assert pre_tokenizers[4].behavior == "isolated"
+
+        assert pre_tokenizers[5].__class__ == Digits
+        pre_tokenizers[5].individual_digits = False
+        assert not pre_tokenizers[5].individual_digits
 
 
 class TestDigits:

bindings/python/tests/bindings/test_processors.py

@@ -227,3 +227,18 @@ class TestSequenceProcessing:
         # assert pair.ids == [1, 2, 3, 4, 5, 0, 6, 0]
         assert pair.type_ids == [0, 0, 0, 0, 0, 0, 1, 1]
         assert pair.offsets == [(0, 0), (0, 2), (3, 7), (8, 10), (12, 16), (0, 0), (0, 4), (0, 0)]
+
+    def test_items(self):
+        processors = Sequence([RobertaProcessing(("</s>", 1), ("<s>", 0)), ByteLevel()])
+        assert processors[0].__class__ == RobertaProcessing
+        assert processors[1].__class__ == ByteLevel
+        processors[0] = ByteLevel(add_prefix_space=False, trim_offsets=False, use_regex=False)
+        print(processors[0])
+        processors[0].add_prefix_space = True
+        processors[0].trim_offsets = True
+        processors[0].use_regex = True
+        print(processors[0])
+        assert processors[0].__class__ == ByteLevel
+        assert processors[0].add_prefix_space
+        assert processors[0].trim_offsets
+        assert processors[0].use_regex

tokenizers/src/normalizers/mod.rs

@@ -43,14 +43,14 @@ impl<'de> Deserialize<'de> for NormalizerWrapper {
     where
         D: Deserializer<'de>,
     {
-        #[derive(Deserialize)]
+        #[derive(Debug, Deserialize)]
         pub struct Tagged {
             #[serde(rename = "type")]
             variant: EnumType,
             #[serde(flatten)]
             rest: serde_json::Value,
         }
-        #[derive(Serialize, Deserialize)]
+        #[derive(Debug, Serialize, Deserialize)]
         pub enum EnumType {
             Bert,
             Strip,
@@ -168,7 +168,7 @@ impl<'de> Deserialize<'de> for NormalizerWrapper {
                     NormalizerUntagged::NFD(bpe) => NormalizerWrapper::NFD(bpe),
                     NormalizerUntagged::NFKC(bpe) => NormalizerWrapper::NFKC(bpe),
                     NormalizerUntagged::NFKD(bpe) => NormalizerWrapper::NFKD(bpe),
-                    NormalizerUntagged::Sequence(bpe) => NormalizerWrapper::Sequence(bpe),
+                    NormalizerUntagged::Sequence(seq) => NormalizerWrapper::Sequence(seq),
                     NormalizerUntagged::Lowercase(bpe) => NormalizerWrapper::Lowercase(bpe),
                     NormalizerUntagged::Nmt(bpe) => NormalizerWrapper::Nmt(bpe),
                     NormalizerUntagged::Precompiled(bpe) => NormalizerWrapper::Precompiled(bpe),

tokenizers/src/normalizers/replace.rs

@@ -46,7 +46,7 @@ impl std::convert::TryFrom<ReplaceDeserializer> for Replace {
 #[serde(tag = "type", try_from = "ReplaceDeserializer")]
 pub struct Replace {
     pattern: ReplacePattern,
-    content: String,
+    pub content: String,
     #[serde(skip)]
     regex: SysRegex,
 }

tokenizers/src/normalizers/utils.rs

@@ -16,16 +16,29 @@ impl Sequence {
     pub fn new(normalizers: Vec<NormalizerWrapper>) -> Self {
         Self { normalizers }
     }
+}
 
-    pub fn get_normalizers(&self) -> &[NormalizerWrapper] {
+impl AsRef<[NormalizerWrapper]> for Sequence {
+    fn as_ref(&self) -> &[NormalizerWrapper] {
         &self.normalizers
     }
+}
 
-    pub fn get_normalizers_mut(&mut self) -> &mut [NormalizerWrapper] {
+impl AsMut<[NormalizerWrapper]> for Sequence {
+    fn as_mut(&mut self) -> &mut [NormalizerWrapper] {
         &mut self.normalizers
     }
 }
 
+impl IntoIterator for Sequence {
+    type Item = NormalizerWrapper;
+    type IntoIter = std::vec::IntoIter<Self::Item>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.normalizers.into_iter()
+    }
+}
+
 impl Normalizer for Sequence {
     fn normalize(&self, normalized: &mut NormalizedString) -> Result<()> {
         for normalizer in &self.normalizers {

tokenizers/src/pre_tokenizers/metaspace.rs

@@ -13,6 +13,12 @@ pub enum PrependScheme {
     Always,
 }
 
+impl std::fmt::Display for PrependScheme {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.serialize(f)
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Serialize, Eq)]
 /// Replaces all the whitespaces by the provided meta character and then
 /// splits on this character

tokenizers/src/pre_tokenizers/punctuation.rs

@@ -12,7 +12,7 @@ fn is_punc(x: char) -> bool {
 #[macro_rules_attribute(impl_serde_type!)]
 pub struct Punctuation {
     #[serde(default = "default_split")]
-    behavior: SplitDelimiterBehavior,
+    pub behavior: SplitDelimiterBehavior,
 }
 
 fn default_split() -> SplitDelimiterBehavior {

tokenizers/src/pre_tokenizers/sequence.rs

@@ -13,16 +13,29 @@ impl Sequence {
     pub fn new(pretokenizers: Vec<PreTokenizerWrapper>) -> Self {
         Self { pretokenizers }
     }
+}
 
-    pub fn get_pre_tokenizers(&self) -> &[PreTokenizerWrapper] {
+impl AsRef<[PreTokenizerWrapper]> for Sequence {
+    fn as_ref(&self) -> &[PreTokenizerWrapper] {
         &self.pretokenizers
     }
+}
 
-    pub fn get_pre_tokenizers_mut(&mut self) -> &mut [PreTokenizerWrapper] {
+impl AsMut<[PreTokenizerWrapper]> for Sequence {
+    fn as_mut(&mut self) -> &mut [PreTokenizerWrapper] {
         &mut self.pretokenizers
     }
 }
 
+impl IntoIterator for Sequence {
+    type Item = PreTokenizerWrapper;
+    type IntoIter = std::vec::IntoIter<Self::Item>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.pretokenizers.into_iter()
+    }
+}
+
 impl PreTokenizer for Sequence {
     fn pre_tokenize(&self, pretokenized: &mut PreTokenizedString) -> Result<()> {
         for pretokenizer in &self.pretokenizers {

tokenizers/src/pre_tokenizers/split.rs

@@ -27,11 +27,11 @@ impl From<&str> for SplitPattern {
 #[derive(Debug, Serialize)]
 #[serde(tag = "type")]
 pub struct Split {
-    pattern: SplitPattern,
+    pub pattern: SplitPattern,
     #[serde(skip)]
-    regex: SysRegex,
-    behavior: SplitDelimiterBehavior,
-    invert: bool,
+    pub regex: SysRegex,
+    pub behavior: SplitDelimiterBehavior,
+    pub invert: bool,
 }
 
 impl<'de> Deserialize<'de> for Split {

tokenizers/src/processors/bert.rs

@@ -6,8 +6,8 @@ use std::iter::FromIterator;
 #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq)]
 #[serde(tag = "type")]
 pub struct BertProcessing {
-    sep: (String, u32),
-    cls: (String, u32),
+    pub sep: (String, u32),
+    pub cls: (String, u32),
 }
 
 impl Default for BertProcessing {
@@ -23,6 +23,14 @@ impl BertProcessing {
     pub fn new(sep: (String, u32), cls: (String, u32)) -> Self {
         Self { sep, cls }
     }
+
+    pub fn get_sep_copy(&self) -> (String, u32) {
+        (self.sep.0.clone(), self.sep.1)
+    }
+
+    pub fn get_cls_copy(&self) -> (String, u32) {
+        (self.cls.0.clone(), self.cls.1)
+    }
 }
 
 #[derive(thiserror::Error, Debug)]

tokenizers/src/processors/roberta.rs

@@ -7,10 +7,10 @@ use std::iter::FromIterator;
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]
 #[serde(tag = "type")]
 pub struct RobertaProcessing {
-    sep: (String, u32),
-    cls: (String, u32),
-    trim_offsets: bool,
-    add_prefix_space: bool,
+    pub sep: (String, u32),
+    pub cls: (String, u32),
+    pub trim_offsets: bool,
+    pub add_prefix_space: bool,
 }
 
 impl Default for RobertaProcessing {
@@ -44,6 +44,14 @@ impl RobertaProcessing {
         self.add_prefix_space = v;
         self
     }
+
+    pub fn get_sep_copy(&self) -> (String, u32) {
+        (self.sep.0.clone(), self.sep.1)
+    }
+
+    pub fn get_cls_copy(&self) -> (String, u32) {
+        (self.cls.0.clone(), self.cls.1)
+    }
 }
 
 impl PostProcessor for RobertaProcessing {

tokenizers/src/processors/sequence.rs

@@ -13,6 +13,39 @@ impl Sequence {
     pub fn new(processors: Vec<PostProcessorWrapper>) -> Self {
         Self { processors }
     }
+
+    pub fn get(&self, index: usize) -> Option<&PostProcessorWrapper> {
+        self.processors.get(index)
+    }
+
+    pub fn get_mut(&mut self, index: usize) -> Option<&mut PostProcessorWrapper> {
+        self.processors.get_mut(index)
+    }
+
+    pub fn set_mut(&mut self, index: usize, post_proc: PostProcessorWrapper) {
+        self.processors[index] = post_proc;
+    }
+}
+
+impl AsRef<[PostProcessorWrapper]> for Sequence {
+    fn as_ref(&self) -> &[PostProcessorWrapper] {
+        &self.processors
+    }
+}
+
+impl AsMut<[PostProcessorWrapper]> for Sequence {
+    fn as_mut(&mut self) -> &mut [PostProcessorWrapper] {
+        &mut self.processors
+    }
+}
+
+impl IntoIterator for Sequence {
+    type Item = PostProcessorWrapper;
+    type IntoIter = std::vec::IntoIter<Self::Item>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.processors.into_iter()
+    }
 }
 
 impl PostProcessor for Sequence {

tokenizers/src/processors/template.rs

@@ -338,7 +338,7 @@ impl From<HashMap<String, SpecialToken>> for Tokens {
 #[builder(build_fn(validate = "Self::validate"))]
 pub struct TemplateProcessing {
     #[builder(try_setter, default = "\"$0\".try_into().unwrap()")]
-    single: Template,
+    pub single: Template,
     #[builder(try_setter, default = "\"$A:0 $B:1\".try_into().unwrap()")]
     pair: Template,
     #[builder(setter(skip), default = "self.default_added(true)")]
@@ -351,6 +351,58 @@ pub struct TemplateProcessing {
     special_tokens: Tokens,
 }
 
+impl TemplateProcessing {
+    // Getter for `single`
+    pub fn get_single(&self) -> String {
+        format!("{:?}", self.single)
+    }
+
+    // Setter for `single`
+    pub fn set_single(&mut self, single: Template) {
+        self.single = single;
+    }
+
+    // Getter for `pair`
+    pub fn get_pair(&self) -> &Template {
+        &self.pair
+    }
+
+    // Setter for `pair`
+    pub fn set_pair(&mut self, pair: Template) {
+        self.pair = pair;
+    }
+
+    // Getter for `added_single`
+    pub fn get_added_single(&self) -> usize {
+        self.added_single
+    }
+
+    // Setter for `added_single`
+    pub fn set_added_single(&mut self, added_single: usize) {
+        self.added_single = added_single;
+    }
+
+    // Getter for `added_pair`
+    pub fn get_added_pair(&self) -> usize {
+        self.added_pair
+    }
+
+    // Setter for `added_pair`
+    pub fn set_added_pair(&mut self, added_pair: usize) {
+        self.added_pair = added_pair;
+    }
+
+    // Getter for `special_tokens`
+    pub fn get_special_tokens(&self) -> &Tokens {
+        &self.special_tokens
+    }
+
+    // Setter for `special_tokens`
+    pub fn set_special_tokens(&mut self, special_tokens: Tokens) {
+        self.special_tokens = special_tokens;
+    }
+}
+
 impl From<&str> for TemplateProcessingBuilderError {
     fn from(e: &str) -> Self {
         e.to_string().into()

tokenizers/src/tokenizer/normalizer.rs

@@ -87,6 +87,12 @@ pub enum SplitDelimiterBehavior {
     Contiguous,
 }
 
+impl std::fmt::Display for SplitDelimiterBehavior {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.serialize(f)
+    }
+}
+
 /// A `NormalizedString` takes care of processing an "original" string to modify
 /// it and obtain a "normalized" string. It keeps both version of the string,
 /// alignments information between both and provides an interface to retrieve