The documentation for "ZipFile.writestr(zinfo_or_arcname, data[, compress_type])" says: "Write the string data to the archive; [...]"
--> https://docs.python.org/3/library/zipfile.html

I fails to mention that data could also be bytes.

The source code does mention it however, that is how I found out:

def writestr(self, zinfo_or_arcname, data, compress_type=None):
        """Write a file into the archive.  The contents is 'data', which
        may be either a 'str' or a 'bytes' instance; if it is a 'str',
        it is encoded as UTF-8 first.
        'zinfo_or_arcname' is either a ZipInfo instance or
        the name of the file in the archive."""

I believe this should be added to the documentation as it's an important information to those who try to add non-UTF8 StringIO data to in-memory ZipFiles using BytesIO.

The change in current PR is very minor and looks good enough that aligns the docs with the docstring and functionality of `ZipFile.writestr` as described.

Can a core-contributor, please look at this?

Also, I'm adding 3.8 for this change.

Since the docstring contains more information, it is better to just copy words from the docstring to the documentation.

There are also other places where string is improperly used instead of bytes or the type is not specified. The note about file name encoding doesn't make sense in Python 3, since ZipFile.write() doesn't support bytes as a file name.

PR 10592 fixed this.

New changeset 4bb186d7e253ad4def875305e06690181e923dfd by Serhiy Storchaka in branch 'master':
bpo-32035: Fix words about strings and bytes in zipfile documentation. (GH-10592)
https://github.com/python/cpython/commit/4bb186d7e253ad4def875305e06690181e923dfd

New changeset af009fbcdb00fffced653792eb7af6b72f2521e3 by Miss Islington (bot) in branch '3.6':
bpo-32035: Fix words about strings and bytes in zipfile documentation. (GH-10592)
https://github.com/python/cpython/commit/af009fbcdb00fffced653792eb7af6b72f2521e3

New changeset 89a3087d40feed3ca78033319389437bb4b5bcd7 by Miss Islington (bot) in branch '3.7':
bpo-32035: Fix words about strings and bytes in zipfile documentation. (GH-10592)
https://github.com/python/cpython/commit/89a3087d40feed3ca78033319389437bb4b5bcd7

messages: + msg330057
versions: + Python 3.8