Best way to generate random file names in Python

You could use the UUID module for generating a random string:

import uuid
filename = str(uuid.uuid4())

This is a valid choice, given that an UUID generator is extremely unlikely to produce a duplicate identifier (a file name, in this case):

Only after generating 1 billion UUIDs every second for the next 100 years, the probability of creating just one duplicate would be about 50%. The probability of one duplicate would be about 50% if every person on earth owns 600 million UUIDs.

Python has facilities to generate temporary file names, see http://docs.python.org/library/tempfile.html. For instance:

In [4]: import tempfile

Each call to tempfile.NamedTemporaryFile() results in a different temp file, and its name can be accessed with the .name attribute, e.g.:

In [5]: tf = tempfile.NamedTemporaryFile()
In [6]: tf.name
Out[6]: 'c:\\blabla\\locals~1\\temp\\tmptecp3i'

In [7]: tf = tempfile.NamedTemporaryFile()
In [8]: tf.name
Out[8]: 'c:\\blabla\\locals~1\\temp\\tmpr8vvme'

Once you have the unique filename it can be used like any regular file. Note: By default the file will be deleted when it is closed. However, if the delete parameter is False, the file is not automatically deleted.

Full parameter set:

tempfile.NamedTemporaryFile([mode='w+b'[, bufsize=-1[, suffix=''[, prefix='tmp'[, dir=None[, delete=True]]]]]])

it is also possible to specify the prefix for the temporary file (as one of the various parameters that can be supplied during the file creation):

In [9]: tf = tempfile.NamedTemporaryFile(prefix="zz")
In [10]: tf.name
Out[10]: 'c:\\blabla\\locals~1\\temp\\zzrc3pzk'

Additional examples for working with temporary files can be found here