Python 3 - Second Edition

24.3    Static Type Checking in Python: mypy

In the previous two sections, we’ve looked at ways to annotate interfaces and definitions with type hints. These annotations are a particularly important source of information for static-type-checking tools.

Such static type checking is performed by an external tool—not by the Python interpreter itself, in that it analyzes the source code of a Python program and checks for possible errors in the use of data types in interfaces. In this case, the analysis is performed statically; that is, the program is not executed.

Such code analysis is often performed implicitly by modern IDEs. Many of them aren’t limited to errors in handling data types; they also recognize other types of errors and error-prone ...