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How to use 2 index variable in a single for loop in python

In C language we can use two index variable in a single for loop like below.

C

for

for (i = 0, j = 0; i < i_max && j < j_max; i++, j++)


Can some one tell how to do this in Python ?

Python

for (i=0, j=0, ...)

3 Answers
3

With zip we can achieve this.

zip

>>> i_max = 5
>>> j_max = 7
>>> for i, j in zip(range(0, i_max), range(0, j_max)):
... print str(i) + ", " + str(j)
...
0, 0
1, 1
2, 2
3, 3
4, 4


If the first answer does not suffice; to account for lists of different sizes, a possible option would be:

a = list(range(5))
b = list(range(15))
for i,j in zip(a+[None]*(len(b)-len(a)),b+[None]*(len(a)-len(b))):
print(i,j)


Or if one wants to cycle around shorter list:

from itertools import cycle

for i,j in zip(range(5),cycle(range(2)):
print(i,j)


You can do this in Python by using the syntax for i,j in iterable:. Of course in this case the iterable must return a pair of values. So for your example, you have to:

for i,j in iterable:

i

j

zip()

for i,j in iterable:

Here is an example:

i_max = 7
j_max = 9

i_values = range(i_max)
j_values = range(j_max)

for i,j in zip(i_values,j_values):
print(i,j)
# 0 0
# 1 1
# 2 2
# 3 3
# 4 4
# 5 5
# 6 6


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