see http://stackoverflow.com/questions/1466000/python-open-built-in-function-difference-between-modes-a-a-w-w-and-r - "The Python docs conveniently leave out the crucial explanation that "open the file for updating" means "opens the file for both reading and writing", which answers my question."

Would you like to propose a patch to the documentation?  It’s possible that “updating” is explained in one place but not everywhere (doc for open, doc for io, doc about file objects).

Is the doc in 3.4 (http://docs.python.org/3.4/library/functions.html#open) clear enough?

If so it could be backported on 2.7/3.3.

yes, "open a disk file for updating (reading and writing)" is a good explanation

This seems to be in 3.3 already, so only 2.7 is left.

I uploaded a patch to reflect reading and writing in the python 2.7 documentation for 'updating'.

New changeset 1f823c1559bd by Éric Araujo in branch '2.7':
Define what “updating” means in docs for open (#19627).
http://hg.python.org/cpython/rev/1f823c1559bd

Edited slightly and committed, thank you!

Can this be closed?