How do you convert a list of strings to a list of floats using Python?

Question

If I have a list of strings:

['   3.2 4.5 7.8 9.2 4.3 4.7 5.2',
'   3.1 4.1 1.3 8.2 4.1 3.2 3.1',
'   3.1 4.2 5.7 3.2 4.1 3.0 1.9']

How can I convert it to a list of floats so my result looks something like this:

[[3.2, 4.5, 7.8, 9.3, 4.3, 4.7, 5.2],
[3.1, 4.1, 1.3, 8.2, 4.1, 3.2, 3.1],
[3.1, 4.2, 5.7, 3.2, 4.1, 3.0, 1.9]]

`print( [list(map(float, i.strip().split())) for i in l] )` – Rakesh Aug 14 '18 at 14:53 — Rakesh, Aug 14 '18 at 14:53
How did this list come to be? – juanpa.arrivillaga Aug 14 '18 at 15:47 — juanpa.arrivillaga, Aug 14 '18 at 15:47

Rakesh · Answer 1 · 2018-08-14T14:56:46.180

3

Use

l = ['   3.2 4.5 7.8 9.2 4.3 4.7 5.2',
'   3.1 4.1 1.3 8.2 4.1 3.2 3.1',
'   3.1 4.2 5.7 3.2 4.1 3.0 1.9']

print( [map(float, i.strip().split()) for i in l] )

Output:

[[3.2, 4.5, 7.8, 9.2, 4.3, 4.7, 5.2], [3.1, 4.1, 1.3, 8.2, 4.1, 3.2, 3.1], [3.1, 4.2, 5.7, 3.2, 4.1, 3.0, 1.9]]

str.split() to split element by space
map(float, 'YOURLIST') to apply float on all elements.

edited Aug 14 '18 at 14:56

answered Aug 14 '18 at 14:53

Rakesh

81,458
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You don't actually need the `list(...)` wrap – dheiberg Aug 14 '18 at 14:56
1

@dheiberg for OP you are correct (Py2.7) but you do in Py3 - `map()` returns an iterator, good to make a note. – AChampion Aug 14 '18 at 14:56
@dheiberg.. Thanks i did not see python2.7 tag. – Rakesh Aug 14 '18 at 14:57

score 1 · Accepted Answer · answered Aug 14 '18 at 14:57

1

You can use below code:

numbers = ['   3.2 4.5 7.8 9.2 4.3 4.7 5.2',
'   3.1 4.1 1.3 8.2 4.1 3.2 3.1',
'   3.1 4.2 5.7 3.2 4.1 3.0 1.9']

print([[float(number) for number in number_list.split()] for number_list in numbers])

answered Aug 14 '18 at 14:57

Rafał

685
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1

It would be more pythonic to use `map` when doing repeated operations on all elements in a list, such as `float()` – Easton Bornemeier Aug 14 '18 at 15:07

How do you convert a list of strings to a list of floats using Python?

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