Missing types

Sometimes, MyPy will complains that it cannot do typechecks for installed package.

… error: Cannot find implementation or library stub for module named ‘…’

See also Missing imports in the MyPu docs.

Missing type hints for built-in module

Update and rerun MyPy.
File a bug report.

Missing type hints for third party library

If the package you installed does not have type annotations built in, then you can do one of the following.

Upgrade the package.
Find stubs that someone wrote for the package and has shared.
Write your own, at least just for the portion of the package that you need.
Add an ignore configuration.

Read on below to see those in more detail.

Upgrade

Upgrade the version of the library you’re using, in case a newer version has started to include type hints.

Find subs

Search to see if there is a PEP 561 compliant stub package, corresponding to your third party library.

Stub packages let you install type hints independently from the library itself.

For example, if you want type hints for the django library, you can install the django-stubs package.

Write stubs

Write your own stub files containing type hints for the library.

You can point mypy at your type hints either by passing them in via the command line, by using the files or mypy_path config file options, or by adding the location to the MYPYPATH environment variable.

These stub files do not need to be complete! A good strategy is to use stubgen, a program that comes bundled with mypy, to generate a first rough draft of the stubs. You can then iterate on just the parts of the library you need.

stubgen in the MyPy docs

With MyPy installed, you can run:

stubgen foo.py

It will generate out/foo.pyi. You should place this in the same directory as the script.

See Specifiying what to stub

See also these to to automatically annotate legacy code, according to the docs:

Configure to ignore

To suppress a single missing import error, add this at the end of the line containing the import:
```
  import foo # type: ignore
```
Handle multi-line import. Note putting the comment after closing bracket doesn’t work.
```
  from foo.bar import (  # type: ignore
      FIZZ,
      BUZZ
  )
```

Add to your MyPy Config file for package foo.

  [mypy-foo.*]
  ignore_missing_imports = True

  [mypy-foo]
  ignore_missing_imports = True

Ignore across libraries:

  [mypy]
  ignore_missing_imports = True