converting each element from string to int in nested list in python

Question

I have data in python with nested lists, a part of which looks like:

data = [['214', '205', '0', '14', '710', '1813494849', '0'], ['214', '204', '0', '30', '710', '1813494856', '0'], ['214', '204', '0', '34', '710', '1813494863', '0'], ['213', '204', '0', '35', '710', '1813494870', '0'], ['213', '203', '0', '35', '710', '1813494877', '0']]

While converting the data using couple methods:

1.

 new_data_list = [[int(x) for x in list] for list in data]

  list=[]
  for i in range(0,len(data)):
      list.append([])
      for j in range(0,len(data[i])):
          b=int(data[i][j])
          list[i].append(b)

I am getting the error which says:

> ValueError: invalid literal for int() with base 10: ''

There are no non-numeric data in my list of data. But there might be something with the header, like an empty header treated as non-numeric value as I have created a list of data from csv.

I wanted to know an efficient way which can convert each element of the list to int while keeping the data multi list.

Side note: *never* shadow built-in `list`, e.g. use `L` or `list_` instead. — jpp, Jan 09 '19 at 11:30
There is nothing wrong with either method that you showed, fundamentally. The problem is that your **actual** data contains empty strings (`''`), which **cannot be converted to `int` individually** like this. — Karl Knechtel, Apr 04 '23 at 05:23

score 7 · Answer 1 · answered Nov 26 '17 at 07:40

7

Call int for each item in each nested list:

new_list = [[int(x) for x in lst] for lst in nested]

Or using map:

new_list = [list(map(int, lst)) for lst in nested]

answered Nov 26 '17 at 07:40

janos

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I tried this but it shows this error: ValueError: invalid literal for int() with base 10: '' – The Novice Programmer Nov 26 '17 at 07:50
@TheNoviceProgrammer it looks like there's a non-numeric value in your input. You should have mentioned that in the question. So now, what would you like to do with non-numeric values? – janos Nov 26 '17 at 07:53
There are no non-numeric values in my data. I think it might me the header which is not visible in the list, as I have created the list of data using readcsv – The Novice Programmer Nov 26 '17 at 08:05
@TheNoviceProgrammer in `data` in the question, there are no non-numeric values, and you should not get any `ValueError`. – janos Nov 26 '17 at 08:32

score 0 · Answer 2 · edited Dec 28 '20 at 00:19

0

A concise one is:

x = ['123', '12', '5']
r = list(map(int, x))
print(r)
>[123, 12, 5]

edited Dec 28 '20 at 00:19

Vivi

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answered Nov 26 '17 at 07:42

user1767754

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converting each element from string to int in nested list in python

2 Answers2

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