davenz davenz - 1 year ago 100
Python Question

Alternative to nesting for loops in Python

I've read that one of the key beliefs of Python is that flat > nested. However, if I have several variables counting up, what is the alternative to multiple for loops?
My code is for counting grid sums and goes as follows:

def horizontal():
for x in range(20):
for y in range(17):
temp = grid[x][y: y + 4]
sum = 0
for n in temp:
sum += int(n)
print sum # EDIT: the return instead of print was a mistype

This seems to me like it is too heavily nested. Firstly, what is considered to many nested loops in Python ( I have certainly seen 2 nested loops before). Secondly, if this is too heavily nested, what is an alternative way to write this code?

Answer Source
from itertools import product

def horizontal():
    for x, y in product(range(20), range(17)):
        print 1 + sum(int(n) for n in grid[x][y: y + 4])

You should be using the sum function. Of course you can't if you shadow it with a variable, so I changed it to my_sum

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