import-outside-top-level (PLC0415)

Derived from the Pylint linter.

This rule is unstable and in preview. The --preview flag is required for use.

What it does

Checks for import statements outside of a module's top-level scope, such as within a function or class definition.

Why is this bad?

PEP 8 recommends placing imports not only at the top-level of a module, but at the very top of the file, "just after any module comments and docstrings, and before module globals and constants."

import statements have effects that are global in scope; defining them at the top level has a number of benefits. For example, it makes it easier to identify the dependencies of a module, and ensures that any invalid imports are caught regardless of whether a specific function is called or class is instantiated.

An import statement would typically be placed within a function only to avoid a circular dependency, to defer a costly module load, or to avoid loading a dependency altogether in a certain runtime environment.

Example

def print_python_version():
    import platform

    print(python.python_version())

Use instead:

import platform


def print_python_version():
    print(python.python_version())