Python: Is there a better way to combine the values of a list -

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• how possible combinations of list’s elements? 15 answers

i'm doing little project class @ university. in 1 of functions have list, like:

x = ["q0", "q1", "q2", "q3", "q4"] 

what want list create dictionary, i'll use store values , values searching in matrix, combine values of list, this:

dic = {("q0", "q1"): "", ("q0", "q2"): "", ... ("q3", "q4"): ""} 

i did way:

part1 = x[1:] part2 = x[:-1] dic = {} v in part1:     r in part2:         if v != r , (r, v) not in dic.keys():             dic[(v, r)] = "" 

i used if because don't want repeated values, like:

("q1", "q1") 

and don't want opposed values, like:

("q2", "q3"), ("q3", "q2") 

my question if there better way of doing this. better using inside for. (when better mean faster) , if there isn't better way, wonder if there more clean way write code. maybe using list comprehension.

you can use itertools.combinations within dict comprehension :

>>> itertools import combinations  >>> x = ["q0", "q1", "q2", "q3", "q4"] >>> d={i:'' in combinations(x,2)} >>> d {('q0', 'q3'): '', ('q2', 'q3'): '', ('q0', 'q2'): '', ('q3', 'q4'): '', ('q1', 'q3'): '', ('q0', 'q4'): '', ('q1', 'q4'): '', ('q0', 'q1'): '', ('q1', 'q2'): '', ('q2', 'q4'): ''}