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+--- Thread: itertools: combinations (/thread-9029.html)
itertools: combinations - Skaperen - Mar-18-2018
i'm looking over the various functions in itertools but i'm not finding what i need.
my use case is to take a list of lists of strings and iterate over the 2nd level to produce a list of the combination of strings. the incoming list might be:
[ ['foo','bar'], ['+','-'], ['corn','wheat','rice'] ]the first 3 and last 3 iterations (in a list) would be:
[ ['foo','+','corn'], ['bar','+','corn'], ['foo','-','corn'], ... ['bar','+','rice'], ['foo','-','rice'], ['bar','-','rice'], ]the whole big list of 12 (in this example) lists is what would be returned. the generator version of this would do a yield of each iteration for a total of 12 yields. better code would be agnostic about what kind of data object or reference is used in place of the strings. i was trying to write this myself. maybe i should go back to that.
RE: itertools: combinations - stranac - Mar-18-2018
You're looking for itertools.product().
>>> import itertools
>>> for x in itertools.product(['foo', 'bar'], ['+', '-'], ['corn', 'wheat', 'rice']):
... print(x)
...
('foo', '+', 'corn')
('foo', '+', 'wheat')
('foo', '+', 'rice')
('foo', '-', 'corn')
('foo', '-', 'wheat')
('foo', '-', 'rice')
('bar', '+', 'corn')
('bar', '+', 'wheat')
('bar', '+', 'rice')
('bar', '-', 'corn')
('bar', '-', 'wheat')
('bar', '-', 'rice')
RE: itertools: combinations - Skaperen - Mar-19-2018
the order is different, but that's ok. itertools.product cycles the last list faster and my example cycles the first list faster. for my needs, it doesn't matter.