Filter a dictionary by certain keys

dictfilter.py

# This code fails because you cannot change a dictionary's size during iteration.

bar = {1: "a",
       2: None,
       3: "c"
}

for key, value in bar.iteritems():
    if value is None:
        bar.pop(key)



# This code achieves the same result, but works.
# Keep in mind, padding function calls' arguments with spaces are not compliant with pep8.
newdict = dict( (key, value) for key, value in bar.iteritems() if key is not None )