>>> import itertools, collections >>> value_to_numeric_map = collections.defaultdict(itertools.count().next) >>> value_to_numeric_map['a'] 0 >>> value_to_numeric_map['b'] 1 >>> value_to_numeric_map['c'] 2 >>> value_to_numeric_map['a'] 0 >>> value_to_numeric_map['b'] 1

>>> a = [random.randint(0, 100) for __ in xrange(100)] >>> heapq.nsmallest(5, a) [3, 3, 5, 6, 8] >>> heapq.nlargest(5, a) [100, 100, 99, 98, 98]

>>> for p in itertools.product([1, 2, 3], [4, 5]): (1, 4) (1, 5) (2, 4) (2, 5) (3, 4) (3, 5) >>> for p in itertools.product([0, 1], repeat=4): ...     print ''.join(str(x) for x in p) ... 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111

>>> for c in itertools.combinations([1, 2, 3, 4, 5], 3): ...     print ''.join(str(x) for x in c) ... 123 124 125 134 135 145 234 235 245 345 >>> for c in itertools.combinations_with_replacement([1, 2, 3], 2): ...     print ''.join(str(x) for x in c) ... 11 12 13 22 23 33

>>> for p in itertools.permutations([1, 2, 3, 4]): ...     print ''.join(str(x) for x in p) ... 1234 1243 1324 1342 1423 1432 2134 2143 2314 2341 2413 2431 3124 3142 3214 3241 3412 3421 4123 4132 4213 4231 4312 4321

>>> a = [1, 2, 3, 4] >>> for p in itertools.chain(itertools.combinations(a, 2), itertools.combinations(a, 3)): ...     print p ... (1, 2) (1, 3) (1, 4) (2, 3) (2, 4) (3, 4) (1, 2, 3) (1, 2, 4) (1, 3, 4) (2, 3, 4) >>> for subset in itertools.chain.from_iterable(itertools.combinations(a, n) for n in range(len(a) + 1)) ...     print subset ... () (1,) (2,) (3,) (4,) (1, 2) (1, 3) (1, 4) (2, 3) (2, 4) (3, 4) (1, 2, 3) (1, 2, 4) (1, 3, 4) (2, 3, 4) (1, 2, 3, 4)

>>> from operator import itemgetter >>> import itertools >>> with open('contactlenses.csv', 'r') as infile: ...     data = [line.strip().split(',') for line in infile] ... >>> data = data[1:] >>> def print_data(rows): ...     print '\n'.join('\t'.join('{: <16}'.format(s) for s in row) for row in rows) ...   >>> print_data(data) young               myope                   no                      reduced                 none young               myope                   no                      normal                  soft young               myope                   yes                     reduced                 none young               myope                   yes                     normal                  hard young               hypermetrope            no                      reduced                 none young               hypermetrope            no                      normal                  soft young               hypermetrope            yes                     reduced                 none young               hypermetrope            yes                     normal                  hard pre-presbyopic      myope                   no                      reduced                 none pre-presbyopic      myope                   no                      normal                  soft pre-presbyopic      myope                   yes                     reduced                 none pre-presbyopic      myope                   yes                     normal                  hard pre-presbyopic      hypermetrope            no                      reduced                 none pre-presbyopic      hypermetrope            no                      normal                  soft pre-presbyopic      hypermetrope            yes                     reduced                 none pre-presbyopic      hypermetrope            yes                     normal                  none presbyopic          myope                   no                      reduced                 none presbyopic          myope                   no                      normal                  none presbyopic          myope                   yes                     reduced                 none presbyopic          myope                   yes                     normal                  hard presbyopic          hypermetrope            no                      reduced                 none presbyopic          hypermetrope            no                      normal                  soft presbyopic          hypermetrope            yes                     reduced                 none presbyopic          hypermetrope            yes                     normal                  none   >>> data.sort(key=itemgetter(-1)) >>> for value, group in itertools.groupby(data, lambda r: r[-1]): ...     print '-----------' ...     print 'Group: ' + value ...     print_data(group) ... ----------- Group: hard young               myope                   yes                     normal                  hard young               hypermetrope            yes                     normal                  hard pre-presbyopic      myope                   yes                     normal                  hard presbyopic          myope                   yes                     normal                  hard ----------- Group: none young               myope                   no                      reduced                 none young               myope                   yes                     reduced                 none young               hypermetrope            no                      reduced                 none young               hypermetrope            yes                     reduced                 none pre-presbyopic      myope                   no                      reduced                 none pre-presbyopic      myope                   yes                     reduced                 none pre-presbyopic      hypermetrope            no                      reduced                 none pre-presbyopic      hypermetrope            yes                     reduced                 none pre-presbyopic      hypermetrope            yes                     normal                  none presbyopic          myope                   no                      reduced                 none presbyopic          myope                   no                      normal                  none presbyopic          myope                   yes                     reduced                 none presbyopic          hypermetrope            no                      reduced                 none presbyopic          hypermetrope            yes                     reduced                 none presbyopic          hypermetrope            yes                     normal                  none ----------- Group: soft young               myope                   no                      normal                  soft young               hypermetrope            no                      normal                  soft pre-presbyopic      myope                   no                      normal                  soft pre-presbyopic      hypermetrope            no                      normal                  soft presbyopic          hypermetrope            no                      normal