Applying a function to values in dict

If you’re using Python 2.7 or 3.x:

d2 = {k: f(v) for k, v in d1.items()}

Which is equivalent to:

d2 = {}
for k, v in d1.items():
    d2[k] = f(v)

Otherwise:

d2 = dict((k, f(v)) for k, v in d1.items())