venv/Lib/site-packages/pip/_internal/utils/packaging.py

import functools
import logging
import re
from typing import NewType, Optional, Tuple, cast

from pip._vendor.packaging import specifiers, version
from pip._vendor.packaging.requirements import Requirement

NormalizedExtra = NewType("NormalizedExtra", str)

logger = logging.getLogger(__name__)


def check_requires_python(
    requires_python: Optional[str], version_info: Tuple[int, ...]
) -> bool:
    """
    Check if the given Python version matches a "Requires-Python" specifier.

    :param version_info: A 3-tuple of ints representing a Python
        major-minor-micro version to check (e.g. `sys.version_info[:3]`).

    :return: `True` if the given Python version satisfies the requirement.
        Otherwise, return `False`.

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

    python_version = version.parse(".".join(map(str, version_info)))
    return python_version in requires_python_specifier


@functools.lru_cache(maxsize=512)
def get_requirement(req_string: str) -> Requirement:
    """Construct a packaging.Requirement object with caching"""
    # Parsing requirement strings is expensive, and is also expected to happen
    # with a low diversity of different arguments (at least relative the number
    # constructed). This method adds a cache to requirement object creation to
    # minimize repeated parsing of the same string to construct equivalent
    # Requirement objects.
    return Requirement(req_string)


def safe_extra(extra: str) -> NormalizedExtra:
    """Convert an arbitrary string to a standard 'extra' name

    Any runs of non-alphanumeric characters are replaced with a single '_',
    and the result is always lowercased.

    This function is duplicated from ``pkg_resources``. Note that this is not
    the same to either ``canonicalize_name`` or ``_egg_link_name``.
    """
    return cast(NormalizedExtra, re.sub("[^A-Za-z0-9.-]+", "_", extra).lower())