The documentation for pickle.dump()

see http://www.python.org/doc/current/lib/node64.html

dump(  	object, file[, protocol[, bin]])

implies that up to four arguments can be specified.
That bin can be specified if protocol has been
specified. The implementation actually accepts only 3
arguments, the last one being either 'protocol' or a
'bin' flag.

The text notation for this function needs to be
clarified, and the visual presentation of the argument
functions changed.

Perhaps to:

dump(  	object, file[, protocol | bin])

or

dump(  	object, file[, protocol] | [, bin])

or

dump(  	object, file[, protocol_or_bin])

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There is one other thing.
The cPickle dump/dumps functions don't like the 'bin'
argument at all:
TypeError: 'bin' is an invalid keyword argument for this
function
They only accept the 'protocol' argument.

So that's another thing that should probably be changed in
cPickle (also see bug 888594), or it should probably be
mentioned in the docs, or the 'bin' argument should be
removed totally ;-)

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The bin parameter has been consistently removed from the
docs as well as from the pickle module in revision 37966.

Resolution should be changed to fixed.

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Python 2.5 docs don't include the "bin" parameter any more.