for line in fileinput.input(files,inplace,backup,"rU"):
  File "/usr/lib/python2.7/fileinput.py", line 253, in next
    line = self.readline()
  File "/usr/lib/python2.7/fileinput.py", line 346, in readline
    self._buffer = self._file.readlines(self._bufsize)
TypeError: an integer is required

According to the documentation, my code was correct. But somewhere along the line, someone added a 'bufsize' parameter and didn't update the docstrings.

It's an easy fix, but I'll have to investigate when this broke.

http://hg.python.org/cpython/file/4dbbf322a9df/Lib/fileinput.py

>In the process, I added an optional bufsize argument to the input()
>function and the FileInput class.

A quick look at the VCS history indicates bufsize has been in there for a long time.  The sphinx docs are wrong as well.  This is correctly documented in python3, apparently as part of the conversion from [] notation to keyword notation in d143eb624cf5.

http://hg.python.org/cpython/file/68c776ba5ea5/Lib/fileinput.py

This is where the incorrect docstrings get added.

Here is a patch against the 2.7 branch.  It will probably also apply to 2.6 if anyone cares.

Oops. I messed up, even on such a tiny fix. #:(

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In the meanwhile, I will fix this. (2.6 is security patches only.)

Your patch missed the doc, as opposed to the docstrings, but your report with tracker research was unusually complete. Thanks.

David, with the addition, this line
    """class FileInput([files[, inplace[, backup[, bufsize[, mode[, openhook]]]]]])
ends at position 83 instead of 80. It should stay on one line. I could reduce that by removing blanks after ,s. Is it better to be a bit too long or a bit too compressed?

At 83 it is a judgement call whether to leave it long or wrap it.  I wouldn't compress it.  (Wrapping is done by putting a '\' at the end of the line you want to wrap, if you don't already know that).

I just remembered: the first list of a .py file docstring should be a one line summary of what the callable does. It should not give the signature because (unlike C function currently) help does that for us from the callable itself (using the inspect module). Putting it in the docstring just repeats it. On 3.3.2:

>>> help(fileinput.input)
Help on function input in module fileinput:

input(files=None, inplace=False, backup='', bufsize=0, mode='r', openhook=None)
    input(files=None, inplace=False, backup="", bufsize=0, mode="r", openhook=None)
...
So the 3.x files need correcting also.
For .doc, the signature does need to be present and correct.

New changeset 80b1c5b25ff0 by Terry Jan Reedy in branch '2.7':
Issue #18315: Improve fileinput docs by adding 'bufsize' where missing and
http://hg.python.org/cpython/rev/80b1c5b25ff0

New changeset 0760b58526ba by Terry Jan Reedy in branch '3.3':
Issue #18315: Improve fileinput docs by adding 'bufsize' where missing and
http://hg.python.org/cpython/rev/0760b58526ba

There was one missing 'bufsize' in 3.x also.