How do I know an item is a directory while looping over zipfile in Python?

Starting with Python 3.6 there is a ZipInfo.is_dir() method.

with zipfile.ZipFile(zip_file) as archive:
    for file in archive.namelist():
        file_info = archive.getinfo(file)
        if file_info.is_dir():
            # do something

See the Python 3.6 docs for details.

Probably this is the right way:

is_dir = lambda zipinfo: zipinfo.filename.endswith('/')