Double for loop list comprehension

Question

I am trying to do following operation using list comprehensions:

Input: [['hello ', 'world '],['foo ',' bar']]
Output: [['hello', 'world'], ['foo', 'bar']]

Here is how one can do it without list comprehensions:

a = [['hello ', 'world '],['foo ',' bar']]
b = []

for i in a:
   temp = []
   for j in i:
      temp.append( j.strip() )
      b.append( temp )

print(b)
#[['hello', 'world'], ['foo', 'bar']]

How can I do it using list comprehensions?

score 2 · Accepted Answer · answered Oct 21 '15 at 01:17

2

a = [['hello ', 'world '],['foo ',' bar']]
b = [[s.strip() for s in l] for l in a]
print(b)
# [['hello', 'world'], ['foo', 'bar']]

answered Oct 21 '15 at 01:17

Mike

19,114
12
59
91

I will accept this since this is the first answer. Thanks. – Sait Oct 21 '15 at 01:22

score 2 · Answer 2 · answered Oct 21 '15 at 01:18

Simply next one list comprehension as each element of a larger list comprehension:

>>> i = [['hello ', 'world '],['foo ',' bar']]
>>> o = [[element.strip() for element in item] for item in i]
>>> o
[['hello', 'world'], ['foo', 'bar']]

Or use list() and map():

>>> i = [['hello ', 'world '],['foo ',' bar']]
>>> o = [list(map(str.strip, item)) for item in i]
>>> o
[['hello', 'world'], ['foo', 'bar']]

score 1 · Answer 3 · answered Oct 21 '15 at 01:19

1

something like this?

input = [['hello ', 'world '], ['foo ',' bar']]

output = [[item.strip() for item in pair] for pair in input]

print output


[['hello', 'world'], ['foo', 'bar']]

answered Oct 21 '15 at 01:19

gary

685
6
14

score 0 · Answer 4 · answered Jan 30 '21 at 04:06

0

grid = [[1,1,0],[0,1,0],[1,0,1]]
visited_arr = [[False for elm in i ]for i in grid]
print(visited_arr)


[[False,False, False],[False,False, False],[False,False, False]]

answered Jan 30 '21 at 04:06

Samarth Singh Thakur

51
4

Welcome to Stack Overflow. Please read [answer]. – ChrisGPT was on strike Jan 30 '21 at 04:27

Double for loop list comprehension

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