Combinations with repetition in python, where order MATTERS
Question:
From python’s Documentation: https://docs.python.org/2/library/itertools.html#itertools.combinations
see combinations_with_replacement: “# combinations_with_replacement(‘ABC’, 2) –> AA AB AC BB BC CC”
I’d like to use the same function, with the bonus of generating “BA”, “CA”, and “CB”.
Answers:
itertools.product is definitely the method you’re looking for here. As the documentation states, it is effectively a compact for loop; product(A,B) is equivalent to ((x, y) for x in A for y in B)
product will return every combination of elements that it can, order-specific, so product('ABC', 'DEF', 'GHI') will get you ADG, ADH, ADI, AEG [...] CFI. If you want to include repetition, you set the optional repeat variable. product(A, repeat=4) is equivalent to product(A,A,A,A). Similarly, product(A, B, repeat=3) is the same as product(A,B,A,B,A,B).
In short: to get the result you’re looking for, call itertools.product('ABC', repeat=2). This will get you tuples AA, AB, AC, BA, BB, BC, CA, CB, CC, in order.
From python’s Documentation: https://docs.python.org/2/library/itertools.html#itertools.combinations
see combinations_with_replacement: “# combinations_with_replacement(‘ABC’, 2) –> AA AB AC BB BC CC”
I’d like to use the same function, with the bonus of generating “BA”, “CA”, and “CB”.
itertools.product is definitely the method you’re looking for here. As the documentation states, it is effectively a compact for loop; product(A,B) is equivalent to ((x, y) for x in A for y in B)
product will return every combination of elements that it can, order-specific, so product('ABC', 'DEF', 'GHI') will get you ADG, ADH, ADI, AEG [...] CFI. If you want to include repetition, you set the optional repeat variable. product(A, repeat=4) is equivalent to product(A,A,A,A). Similarly, product(A, B, repeat=3) is the same as product(A,B,A,B,A,B).
In short: to get the result you’re looking for, call itertools.product('ABC', repeat=2). This will get you tuples AA, AB, AC, BA, BB, BC, CA, CB, CC, in order.