Thanks for the report!

The default values of fp and environ parameters are already documented in the function signature in Python 3:

    cgi.parse(fp=None, environ=os.environ, keep_blank_values=False, strict_parsing=False)

In Python 2, the function signature is:

    cgi.parse(fp[, environ[, keep_blank_values[, strict_parsing]]])

Since the default values cannot be documented in the latter form, we need to specify them separately in plain text.

The reason why "(the file defaults to ``sys.stdin``)" is still in Python 3 documentation is because of the following two lines in cgi.parse() implementation:

    if fp is None:
        fp = sys.stdin

So if you invoke cgi.parse() (which means fp is None) it will be replaced with sys.stdin.