diff --git a/.github/workflows/python-publish.yml b/.github/workflows/python-publish.yml
new file mode 100644
index 0000000..5cec857
--- /dev/null
+++ b/.github/workflows/python-publish.yml
@@ -0,0 +1,42 @@
+# This workflow will upload a Python Package using Twine when a release is created
+# For more information see: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-python#publishing-to-package-registries
+
+# This workflow uses actions that are not certified by GitHub.
+# They are provided by a third-party and are governed by
+# separate terms of service, privacy policy, and support
+# documentation.
+
+name: Upload Python Package
+
+on:
+  release:
+    types: [published]
+
+permissions:
+  contents: read
+
+env:
+  PYPI_API_TOKEN: ${{ secrets.PYPI_API_TOKEN }}
+  
+jobs:
+  deploy:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+    - name: Set up Python
+      uses: actions/setup-python@v3
+      with:
+        python-version: '3.8'
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        python -m pip install --upgrade build
+        pip install twine
+    - name: Build package
+      run: |
+        python -m build
+    - name: Upload to PyPi
+      run: |
+          twine upload dist/* -u __token__ -p "$PYPI_API_TOKEN"
\ No newline at end of file
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..af8394f
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+build
+tokenizer_adapter.egg-info
+__pycache__
+*/**/__pycache__
+tokenizer_adapter/eval_adapter.py
+tokenizer_adapter/test_adapter.py
\ No newline at end of file
diff --git a/LICENSE b/LICENSE
index 261eeb9..45bc4a1 100644
--- a/LICENSE
+++ b/LICENSE
@@ -186,7 +186,7 @@
       same "printed page" as the copyright notice for easier
       identification within third-party archives.
 
-   Copyright [yyyy] [name of copyright owner]
+   Copyright [2024] [Charles Condevaux]
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..0333b54
--- /dev/null
+++ b/README.md
@@ -0,0 +1,38 @@
+# Tokenizer Adapter
+
+A simple tool to adapt a pretrained Huggingface model to a new vocabulary (domain specific) with (almost) no training. \
+Should work for almost all language models from the Huggingface Hub (need more test).
+
+## Install
+
+```
+pip install 
+```
+
+## Usage
+```python
+from tokenizer_adapter import TokenizerAdapter
+from transformers import AutoTokenizer, AutoModelForMaskedLM
+
+BASE_MODEL_PATH = "camembert-base"
+
+# A simple corpus
+corpus = ["A first sentence", "A second sentence", "blablabla"]
+
+# Load model and tokenizer
+model = AutoModelForMaskedLM.from_pretrained(BASE_MODEL_PATH)
+tokenizer = AutoTokenizer.from_pretrained(BASE_MODEL_PATH)
+
+# Train new vocabulary from the old tokenizer
+new_tokenizer = tokenizer.train_new_from_iterator(corpus, vocab_size=300)
+
+# Default params should work in most cases
+adapter = TokenizerAdapter()
+
+# Patch the model with the new tokenizer
+model = adapter.adapt_from_pretrained(new_tokenizer, model, tokenizer)
+
+# Save the model and the new tokenizer
+model.save_pretrained("my_new_model/")
+new_tokenizer.save_pretrained("my_new_model/")
+```
\ No newline at end of file
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..4ac16fd
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,3 @@
+[build-system]
+requires = ["setuptools>=61.0.0", "torch>=1.8", "tokenizers>=0.15.0", "tqdm"]
+build-backend = 'setuptools.build_meta'
\ No newline at end of file
diff --git a/requirements b/requirements
new file mode 100644
index 0000000..e69de29
diff --git a/setup.cfg b/setup.cfg
new file mode 100644
index 0000000..72a5be6
--- /dev/null
+++ b/setup.cfg
@@ -0,0 +1,23 @@
+[metadata]
+name = tokenizer-adapter
+version = 0.1.0
+author = Charles Condevaux
+author_email = charles.condevaux@gmail.com
+description = Tools to adapt a pretrained model to a new vocabulary
+long_description = file: README.md
+long_description_content_type = text/markdown
+url = https://github.com/ccdv-ai/tokenizer-adapter
+classifiers =
+    Programming Language :: Python :: 3
+    License :: OSI Approved :: MIT License
+    Operating System :: OS Independent
+
+[options]
+packages = find:
+python_requires = >=3.8
+include_package_data = True
+install_requires = 
+    torch>=1.8
+    tokenizers>=0.15.0
+    tqdm
+    
\ No newline at end of file
diff --git a/tokenizer_adapter/__init__.py b/tokenizer_adapter/__init__.py
new file mode 100644
index 0000000..56ac82f
--- /dev/null
+++ b/tokenizer_adapter/__init__.py
@@ -0,0 +1 @@
+from .adapter import *
\ No newline at end of file
diff --git a/tokenizer_adapter/adapter.py b/tokenizer_adapter/adapter.py
new file mode 100644
index 0000000..5ec8dbe
--- /dev/null
+++ b/tokenizer_adapter/adapter.py
@@ -0,0 +1,228 @@
+import torch 
+import tqdm 
+from copy import deepcopy
+from math import sqrt
+from tokenizers import normalizers
+from tokenizers import pre_tokenizers
+from tokenizers import decoders
+
+class TokenizerAdapter():
+
+    def __init__(self, method="average", clean_tokenizer=False, custom_preprocessing=None) -> None:
+        """
+        Adapter an existing model with a new tokenizer
+        Args:
+            method (`str`, *optional*, defaults to 'average'):
+                Method to use to merge tokens. In ["average", "bos", "frequency", "reverse_frequency", "inverse_frequency"]
+            clean_tokenizer (`bool`, *optional*, defaults to False):
+                Remove the normalizer, the pre_tokenizer and the decoder in the old tokenizer (experimental)
+            custom_preprocessing (`function`, *optional*, defaults to None):
+                A custom function to apply some normalization before feeding tokens from the new vocabulary to the old tokenizer.
+                Example replacing a metaspace by a RoBERTa separator: lambda x: x.replace("▁", "Ġ")
+        """
+        assert method in ["average", "bos", "frequency", "reverse_frequency", "inverse_frequency"]
+        self.method = method
+        self.process_function = {
+            "average": self.process_average, 
+            "bos": self.process_bos,
+            "frequency": self.process_frequency,
+            "reverse_frequency": self.process_reverse_frequency,
+            "inverse_frequency": self.process_inverse_frequency
+            }[self.method]
+        self.clean_tokenizer = clean_tokenizer
+    
+    def get_state_dict_keys_to_update(self, state_dict, vocab_size):
+
+        state_dict_to_update = {}
+        for key, tensor in state_dict.items():
+            if vocab_size in tensor.shape:
+                state_dict_to_update[key] = tensor
+        return state_dict_to_update
+
+    def prepare_correspondance_dict(self, new_tokenizer, old_tokenizer):
+
+        vocab_size = len(new_tokenizer.vocab.keys())
+        old_vocab_size = len(old_tokenizer.vocab.keys())
+        frequency_matrix = None 
+        
+        unk_token_id = old_tokenizer.unk_token_id
+        if unk_token_id is None:
+            unk_token_id = old_tokenizer.pad_token_id
+        if unk_token_id is None:
+            unk_token_id = old_tokenizer.eos_token_id
+
+        if self.method in ["frequency", "reverse_frequency", "inverse_frequency"]:
+            frequency_matrix = torch.zeros(old_vocab_size)
+
+        correspondance_dict = {"pairs": {}, "meta": {}}
+
+        # Loop over the new vocabulary
+        for new_token, i in tqdm.tqdm(new_tokenizer.vocab.items()):
+
+            old_token_ids = old_tokenizer.convert_tokens_to_ids([new_token])
+            # if token doesnt exist in old vocab
+            if len(old_token_ids) == 0 or (len(old_token_ids) == 1 and old_token_ids[0] == unk_token_id):
+                # untokenize new_token
+                new_token = new_tokenizer.convert_tokens_to_string([new_token])
+                old_token_ids = old_tokenizer.encode(new_token, add_special_tokens=False)
+            
+            old_token_ids = [t if t < old_vocab_size else unk_token_id for t in old_token_ids]
+            correspondance_dict["pairs"][str(i)] = old_token_ids
+
+            # Fill frequency matrix
+            if frequency_matrix is not None and len(old_token_ids) > 1:
+                for t in old_token_ids:
+                    frequency_matrix[t] += 1
+
+        correspondance_dict["meta"]["vocab_size"] = vocab_size
+        correspondance_dict["meta"]["old_vocab_size"] = old_vocab_size
+        correspondance_dict["meta"]["frequency_matrix"] = frequency_matrix
+
+        correspondance_dict["meta"]["old_bos_token_id"] = old_tokenizer.bos_token_id
+        correspondance_dict["meta"]["bos_token_id"] = new_tokenizer.bos_token_id
+        correspondance_dict["meta"]["old_eos_token_id"] = old_tokenizer.eos_token_id
+        correspondance_dict["meta"]["eos_token_id"] = new_tokenizer.eos_token_id
+        correspondance_dict["meta"]["old_pad_token_id"] = old_tokenizer.pad_token_id
+        correspondance_dict["meta"]["pad_token_id"] = new_tokenizer.pad_token_id
+
+        return correspondance_dict
+
+    def process_tensors(self, state_dict, correspondance_dict):
+        vocab_size = correspondance_dict["meta"]["old_vocab_size"]
+
+        for tensor_key, tensor in state_dict.items():
+            
+            print("Processing: ", tensor_key)
+            do_transpose = False
+            if len(tensor.size()) > 1 and tensor.size()[-1] == vocab_size:
+                do_transpose = True
+                tensor = tensor.T
+
+            new_tensor = self.process_single_tensor(tensor, correspondance_dict)
+            state_dict[tensor_key] = new_tensor.T if do_transpose else new_tensor
+        
+        return state_dict
+    
+    def process_single_tensor(self, tensor, correspondance_dict):
+
+        vocab_size = correspondance_dict["meta"]["vocab_size"]
+
+        if len(tensor.size()) > 1:
+            new_tensor = torch.zeros(vocab_size, tensor.size()[-1], dtype=tensor.dtype)
+        else:
+            new_tensor = torch.zeros(vocab_size, dtype=tensor.dtype)
+
+        for new_idx, old_idx in tqdm.tqdm(correspondance_dict["pairs"].items()):
+            new_idx = int(new_idx)
+            value = self.process_function(old_idx, tensor, correspondance_dict["meta"])
+            new_tensor[new_idx] = value
+        return new_tensor
+
+    def process_average(self, old_idx, tensor, meta_dict):
+        new_tensor = tensor[old_idx].mean(dim=0)
+        return new_tensor
+    
+    def process_bos(self, old_idx, tensor, meta_dict):
+
+        bos = tensor[meta_dict["old_bos_token_id"]]
+        new_tensor = tensor[old_idx]
+        if len(bos.size()) == 0:
+            bos = bos.unsqueeze(-1)
+            new_tensor = new_tensor.unsqueeze(-1)
+        new_tensor = torch.softmax(bos @ new_tensor.T / sqrt(bos.size()[0]), dim=-1) @ new_tensor
+        return new_tensor
+    
+    def process_frequency(self, old_idx, tensor, meta_dict):
+        
+        frequencies = meta_dict["frequency_matrix"] / meta_dict["frequency_matrix"].sum() + 1e-8
+        frequencies = frequencies[old_idx]
+        frequencies = frequencies / frequencies.sum()
+        new_tensor = tensor[old_idx]
+
+        if len(new_tensor.size()) == 1:
+            new_tensor = new_tensor.unsqueeze(-1)
+        new_tensor = (new_tensor * frequencies.unsqueeze(-1)).sum(dim=0)
+        return new_tensor
+    
+    def process_reverse_frequency(self, old_idx, tensor, meta_dict):
+        
+        frequencies = meta_dict["frequency_matrix"] / meta_dict["frequency_matrix"].sum() + 1e-8
+        frequencies = 1 - frequencies[old_idx]
+        frequencies = frequencies / frequencies.sum()
+        new_tensor = tensor[old_idx]
+
+        if len(new_tensor.size()) == 1:
+            new_tensor = new_tensor.unsqueeze(-1)
+        new_tensor = (new_tensor * frequencies.unsqueeze(-1)).sum(dim=0)
+        return new_tensor
+    
+    def process_inverse_frequency(self, old_idx, tensor, meta_dict):
+        
+        frequencies = meta_dict["frequency_matrix"] / meta_dict["frequency_matrix"].sum() + 1e-8
+        frequencies = 1 / frequencies[old_idx]
+        frequencies = frequencies / frequencies.sum()
+        new_tensor = tensor[old_idx]
+
+        if len(new_tensor.size()) == 1:
+            new_tensor = new_tensor.unsqueeze(-1)
+        new_tensor = (new_tensor * frequencies.unsqueeze(-1)).sum(dim=0)
+        return new_tensor
+
+    def merge_dict(self, state_dict, state_dict_keys_updated):
+
+        for key, value in state_dict_keys_updated.items():
+            requires_grad = state_dict[key].requires_grad
+            state_dict[key] = value
+        return state_dict
+    
+    def prepare_new_config(self, config, correspondance_dict):   
+        config.pad_token_id = correspondance_dict["meta"]["pad_token_id"]
+        config.bos_token_id = correspondance_dict["meta"]["bos_token_id"]
+        config.eos_token_id = correspondance_dict["meta"]["eos_token_id"]
+        config.vocab_size = correspondance_dict["meta"]["vocab_size"]
+        return config
+
+    def adapt_from_pretrained(self, new_tokenizer, model, tokenizer, **kwargs):
+        
+        """
+        Adapt a new model from a pretrained model and a pretrained tokenizer
+        Args:
+            new_tokenizer (`PreTrainedTokenizer`):
+                The new tokenizer trained on a specific corpus
+            model (`PreTrainedModel`):
+                The pretrained model to modify
+            tokenizer (`PreTrainedTokenizer`):
+                The tokenizer of the pretrained model
+        """
+
+        if self.clean_tokenizer:
+            tokenizer._tokenizer.normalizer = normalizers.Sequence([])
+            tokenizer._tokenizer.pre_tokenizer = pre_tokenizers.Sequence([])
+            tokenizer._tokenizer.decoder = decoders.Sequence([])
+
+        with torch.no_grad():
+            #state_dict = deepcopy(model.state_dict())
+            state_dict = model.state_dict()
+            config = deepcopy(model.config)
+            config_vocab_size = model.config.vocab_size
+            #del model
+
+            # Select keys to update
+            state_dict_keys_to_update = self.get_state_dict_keys_to_update(state_dict, config_vocab_size)
+            if len(state_dict_keys_to_update.keys()) == 0:
+                state_dict_keys_to_update = self.get_state_dict_keys_to_update(state_dict, len(tokenizer.vocab.keys()))
+
+            # Create correspondance table
+            correspondance_dict = self.prepare_correspondance_dict(new_tokenizer, tokenizer)
+
+            # Update config
+            config = self.prepare_new_config(config, correspondance_dict)
+            # Update tensors
+            state_dict_keys_to_update = self.process_tensors(state_dict_keys_to_update, correspondance_dict)
+            # Merge in state dict
+            state_dict = self.merge_dict(state_dict, state_dict_keys_to_update)
+
+            model = model.from_pretrained(pretrained_model_name_or_path=None, config=config, state_dict=state_dict)
+
+        return model
+