How to convert a list of string to a list of int

Question

I have this list in a list

a = [['1','2','3','4'],['1','2','3','4'],['1','2','3','4']]

but i need it to be ints , im not sure where to use int() to change str to int

a = [[1,2,3,4],[1,2,3,4],[1,2,3,4]]

Yudhishthir Singh · Accepted Answer · 2012-12-02 19:30:26Z

3

You can use a nested list comprehension like so:

a = [['1','2','3','4'],['1','2','3','4'],['1','2','3','4']]
b = [ [int(j) for j in i] for i in a]

answered Dec 2, 2012 at 19:30

Yudhishthir Singh

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NPE · Accepted Answer · 2012-12-02 19:34:46Z

1

In [51]: a = [['1','2','3','4'],['1','2','3','4'],['1','2','3','4']]

In [52]: [map(int, l) for l in a]
Out[52]: [[1, 2, 3, 4], [1, 2, 3, 4], [1, 2, 3, 4]]

answered Dec 2, 2012 at 19:34

NPE

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Lev Levitsky · Accepted Answer · 2012-12-02 19:29:51Z

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An example using nested list comprehension:

In [1]: a = [['1','2','3','4'],['1','2','3','4'],['1','2','3','4']]

In [2]: [[int(s) for s in l] for l in a]
Out[2]: [[1, 2, 3, 4], [1, 2, 3, 4], [1, 2, 3, 4]]

answered Dec 2, 2012 at 19:29

Lev Levitsky

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arshajii · Accepted Answer · 2012-12-02 19:37:18Z

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Here's an idea:

>>> a = [['1','2','3','4'],['1','2','3','4'],['1','2','3','4']]
>>> map(lambda l: map(int, l), a)
[[1, 2, 3, 4], [1, 2, 3, 4], [1, 2, 3, 4]]

answered Dec 2, 2012 at 19:37

arshajii

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