**Breaking changes:**
- isort now requires Python 3.6+ to run but continues to support formatting on ALL versions of python including
Python 2 code.
- isort deprecates official support for Python 3.4, removing modules only in this release from known_standard_library:
- user
- Config files are no longer composed on-top of each-other. Instead the first config file found is used.
- Since there is no longer composition negative form settings (such as --dont-skip or it's config file variant `not_skip`) are no longer required and have been removed.
- Two-letter shortened setting names (like `ac` for `atomic`) now require two dashes to avoid ambiguity: `--ac`.
- For consistency with other tools `-v` now is shorthand for verbose and `-V` is shorthand for version. See Issue: 1067.
- `length_sort_{section_name}` config usage has been deprecated. Instead `length_sort_sections` list can be used to specify a list of sections that need to be length sorted.
- `safety_excludes` and `unsafe` have been deprecated
- Config now includes as default full set of safety directories defined by safety excludes.
- `--recursive` option has been removed. Directories passed in are now automatically sorted recursive.
- `--apply` option has been removed as it is the default behaviour.
- isort now does nothing, beyond giving instructions and exiting status code 0, when ran with no arguments.
- a new `--interactive` flag has been added to enable the old style behaviour.
- isort now works on contiguous sections of imports, instead of one whole file at a time.
- ~~isort now formats all nested "as" imports in the "from" form. `import x.y as a` becomes `from x import y as a`.~~ NOTE: This was undone in version 5.1.0 due to feedback it caused issues with some project conventions.
- `keep_direct_and_as_imports` option now defaults to `True`.
- `appdirs` is no longer supported. Unless manually specified, config should be project config only.
- `toml` is now installed as a vendorized module, meaning pyproject.toml based config is always supported.
- Completely new Python API, old version is removed and no longer accessible.
- New module placement logic and module fully replaces old finders. Old approach is still available via `--old-finders`.
Internal:
- isort now utilizes mypy and typing to filter out typing related issues before deployment.
- isort now utilizes black internally to ensure more consistent formatting.
- profile support for common project types (black, django, google, etc)
- Much much more. There is some difficulty in fully capturing the extent of changes in this release - just because of how all encompassing the release is. See: [Github Issues](https://github.com/pycqa/isort/issues?q=is%3Aissue+is%3Aclosed) for more.