Please don't close this as "invalid."

Most (all?) of the functions in the os module have positional-only arguments, which are documented in exactly the same manner as arguments which can be supplied using a keyword.

As someone reading the documentation, how am I supposed to know which arguments can be supplied with keywords and which can't?

This ticket and the link to http://docs.python.org/dev/reference/expressions.html#calls are helpful in explaining this now, but I would NEVER have thought to look there to find out why os.fdopen isn't working the way it's documented. Requiring me to experiment to determine which function works which way seems to miss the point of having documentation in the first place.

I take no position on whether this should be fixed with a documentation change or a code change, but it should be fixed. If the consensus is that a documentation change would be quicker to implement, I'm happy to submit a doc patch.