In C language we can use two index variable in a single for loop like below.
for (i = 0, j = 0; i < i_max && j < j_max; i++, j++)
Can some one tell how to do this in Python ?
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Take a look here.Vasilis G.– Vasilis G.2018-08-08 13:32:49 +00:00Commented Aug 8, 2018 at 13:32
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Yes, I got it. With zip we can do this.rashok– rashok2018-08-08 13:36:31 +00:00Commented Aug 8, 2018 at 13:36
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2Possible duplicate of "for loop" with two variables?MooingRawr– MooingRawr2018-08-08 13:36:44 +00:00Commented Aug 8, 2018 at 13:36
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4 Answers
With zip we can achieve this.
>>> 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
2 Comments
sdgaw erzswer
I would not agree. This does not account for different-sized lists, does it?
Sagar Dawda
Good solution by @rashok . Works well for equal sized list. If you wanted a dataframe, you could create a tuple of (i, j) and append to a list. That list can be used to create a dataframe.
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)
Comments
One possible way to do that is to iterate over a comprehensive list of lists. For example, if you want to obtain something like
for r in range(1, 3):
for c in range(5, 7):
print(r, c)
which produces
# 1 5
# 1 6
# 2 5
# 2 6
is by using
for i, j in [[_i, _j] for _i in range(1, 3) for _j in range(5, 7)]:
print(i, j)
Maybe, sometimes one more line is not so bad.
Comments
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:
- define the list of values for
iand forj - build the iterable returning a pair of values from both lists:
zip()is your friend in this case (if the lists have different sizes, it stops at the last element of the shortest one) - use the syntax
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
1 Comment
Sagar Dawda
same answer as provided by @rashok