def check_requires_python(requires_python):
    # type: (Optional[str]) -> bool
    """
    Check if the python version in use match the `requires_python` specifier.

    Returns `True` if the version of python in use matches the requirement.
    Returns `False` if the version of python in use does not matches the
    requirement.

    Raises an InvalidSpecifier if `requires_python` have an invalid format.
    """
    if requires_python is None:
        # The package provides no information
        return True
    requires_python_specifier = specifiers.SpecifierSet(requires_python)

    # We only use major.minor.micro
    python_version = version.parse('.'.join(map(str, sys.version_info[:3])))
    return python_version in requires_python_specifier

    Check if the python version in use match the `requires_python` specifier.

    Returns `True` if the version of python in use matches the requirement.
    Returns `False` if the version of python in use does not matches the
    requirement.

    Raises an InvalidSpecifier if `requires_python` have an invalid format.
    
stackoverflow/venv/lib/python3.6/site-packages/pip-19.0.3-py3.6.egg/pip/_internal/utils/packaging.py