python - How can mypy ignore a single line in a source file?

84
votes

I'm using mypy in my python project for type checking. I'm also using PyYAML for reading and writing the project configuration files. Unfortunately, when using the recommended import mechanism from the PyYAML documentation this generates a spurious error in a try/except clause that attempts to import native libraries:

from yaml import load, dump
try:
    from yaml import CLoader as Loader, CDumper as Dumper
except ImportError:
    from yaml import Loader, Dumper

On my system CLoader and CDumper aren't present, which results in the errors error: Module 'yaml' has no attribute 'CLoader' and error: Module 'yaml' has no attribute 'CDumper'.

Is there a way to have mypy ignore errors on this line? I was hoping that I could do something like this to have mypy skip that line:

from yaml import load, dump
try:
    from yaml import CLoader as Loader, CDumper as Dumper  # nomypy
except ImportError:
    from yaml import Loader, Dumper
3
pythontypesmypy

3 Answers

109
votes

You can ignore type errors with # type: ignore as of version 0.2 (see issue #500, Ignore specific lines):

PEP 484 uses # type: ignore for ignoring type errors on particular lines ...

Also, using # type: ignore close to the top of a file [skips] checking that file altogether.

Source: mypy#500

18
votes

Also # mypy: ignore-errors at the top of the file you want to ignore all works, if you are using shebang and coding lines should be like this:

#!/usr/bin/env python 
#-*- coding: utf-8 -*-
# mypy: ignore-errors

Gvanrossum comment

3
votes

I would rather config it in mypy.ini

For example, to ignore Django migrations:

[mypy-*.migrations.*]
ignore_errors = True