__init__.py 文件源码

def parse_requirement_line(line, filename, line_number, session, finder):
    """Parse a requirement line and return an InstallRequirement instance.

    :param line:         One line from a requirements.txt file.
    :param filename:     Path to a requirements.txt file.
    :param line_number:  The integer line number of the current line.
    :param session:      Instance of pip.download.PipSession.
    :param finder:       Instance of pip.download.PackageFinder.
    """

    if not line:
        return None

    reqs = list(req_file.process_line(
                line, filename, line_number, session=session, finder=finder))
    return reqs[0] if len(reqs) > 0 else None