itertools

More efficient versions of built-in functions

• ifilter
• imap
• islice
• izip

Other very useful functionality

• chain - combine multiple iterables to look like one
• count - just like our counter (but without stop or by arguments)
• repeat - return the given argument repeatedly
• more...

Combining multiple itertools functions

numbers = "zero one two three".split()
for number, word in izip(count(), numbers):
    print "%d = %s" % (number, word)
# Result:
# 0 = zero
# 1 = one
# 2 = two
# 3 = three

for number, word in izip(xrange(10), chain(numbers, repeat("unknown"))):
    print "%d = %s" % (number, word)
# Result:
# 0 = zero
# 1 = one
# 2 = two
# 3 = three
# 4 = unknown
# 5 = unknown
# 6 = unknown
# 7 = unknown
# 8 = unknown
# 9 = unknown