I’m willing to make a program that evaluates all possible combinations of operations ( + , – , * , / ) on a set of positive integers of length 6 (eg : [1, 6, 3, 9, 2, 9] ).
To do so, I am using the list
symbols = ['+', '-', '*', '/']
and wrote a nested loop to create all possibilities
+ + + + + + + + + - . . . / / / / * / / / / /
by calling each row (eg : + – + * / ) a motif, and M the set of all motifs where
M[0] = ['+', '+', '+', '+', '+'] M[1] = ['+', '+', '+', '+', '-']
and so on. My goal now would be to write a function
evaluate_expression(motif, a, b, c, d, e, f)
that spits out the result of the expression a motif[0] b motif[1] c motif[2] d motif[3] e motif[4] f
my idea was to try converting ‘+’ into the symbol + but I couldn’t find a way to do it, I hope some of you guys here would know how to do that, I’m open to any suggestion of modification to make this cleaner.
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Answer
The operator library gives you functions for the basic operators (e.g. add(), sub())
So, you could replace your symbols = ['+', '-', '*', '/'] with:
from operator import add, sub, mul, truediv symbols = [add, sub, mul, truediv]
and now your motif-generating function should make lists of functions instead of lists of strings.
Then, assuming you have a motif list, as you call it (check out itertools.combinations_with_replacement() for a function to generate all motifs), you can apply it by doing something like:
motif = [add, add, sub]
values = [5, 6, 7, 8]
result = values[0]
for i, current_func in enumerate(motif):
result = current_func(result, value[i+1])
print(result)
Note: this method will not respect order of operations, it will apply the functions in order, left to right.