How imports are found

When mypy encounters an import statement or receives modulenames from the command line via the —module or —packageflags, mypy tries to find the module on the file system similarto the way Python finds it. However, there are some differences.

First, mypy has its own search path.This is computed from the following items:

• The MYPYPATH environment variable(a colon-separated list of directories).
• The mypy_path config file option.
• The directories containing the sources given on the command line(see below).
• The installed packages marked as safe for type checking (seePEP 561 support)
• The relevant directories of thetypeshed repo.

Note

You cannot point to a PEP 561 package via the MYPYPATH, it must beinstalled (see PEP 561 support)

For sources given on the command line, the path is adjusted by crawlingup from the given file or package to the nearest directory that does notcontain an init.py or init.pyi file. If the given pathis relative, it will only crawl as far as the current working directory.

Second, mypy searches for stub files in addition to regular Python filesand packages.The rules for searching for a module foo are as follows:

• The search looks in each of the directories in the search path(see above) until a match is found.
• If a package named foo is found (i.e. a directoryfoo containing an init.py or init.pyi file)that’s a match.
• If a stub file named foo.pyi is found, that’s a match.
• If a Python module named foo.py is found, that’s a match.

These matches are tried in order, so that if multiple matches are foundin the same directory on the search path(e.g. a package and a Python file, or a stub file and a Python file)the first one in the above list wins.

In particular, if a Python file and a stub file are both present in thesame directory on the search path, only the stub file is used.(However, if the files are in different directories, the one foundin the earlier directory is used.)