# Hugging Face Transformers v4.0.0 — Release & Upgrade Intelligence
- **Product:** Hugging Face Transformers (https://huggingface.co)
- **Version:** v4.0.0
- **Released:** Nov 30, 2020
- **Impact Score:** 7/10
- **Breaking Changes:** Source flagged
- **Canonical Analysis:** https://changelogs.us/transformers/updates/v4.0.0/

## Executive Summary (TL;DR)
Hugging Face Transformers v4.0.0. Source highlight: Transformers v4.0.0-rc-1: Fast tokenizers, model outputs, file reorganization

## Breaking Changes & Deprecations
- Breaking changes since v3.x Version v4.0.0 introduces several breaking changes that were necessary.
- Version v4.0.0 introduces several breaking changes that were necessary.
- The python and rust tokenizers have roughly the same API, but the rust tokenizers have a more complete feature set. The main breaking change is the handling of overflowing tokens between the python and rust tokenizers.
- This is a breaking change as importing intermediary layers using a model's module directly needs to be done via a different path.
- This is a breaking change as the limitation of that tuple is that it cannot be unpacked: `value0, value1 = outputs` will not work.
- - [breaking|pipelines|tokenizers] Adding slow-fast tokenizers equivalence tests pipelines - Removing sentencepiece as a required dependency #8073 (@thomwolf)

## New Features
- The pipelines now contain additional features out of the box. See the token-classification pipeline with the `grouped_entities` flag.
- Add TFDPR #8203 (@ratthachat)

## Bug Fixes
- Fix init for MT5 #8591 (@sgugger)
- [s2s/distill] hparams.tokenizer_name = hparams.teacher #8382 (@ShichaoSun)
- [examples] better PL version check #8429 (@stas00)
- Question template #8440 (@sgugger)
- [docs] improve bart/marian/mBART/pegasus docs #8421 (@sshleifer)
- Add auto next sentence prediction #8432 (@jplu)

## Upgrade Command
```bash
python -m pip install 'transformers==4.0.0'
```