Convert measurement from String to Int or Float

Question

I have the string

var = '7 msecs'
#var = int(var)
#var = float(var)

And I want to convert that to an integer (7), or float (7.0). This conversion works in javascript, as it seems to take the first value before the following, non-numerical values.

How can I do this in Python?

I want a good way to do this, without having to do

var = int(var.split(' ')[0])

It should also work for:

'10mm' or '10.55€'

Considered duplicate (Python: Extract numbers from a string)

This question is different, as I'm trying to replicate the ability of parseInt/parseFloat in javascript which only returns the numbers at the beginning of a string. This other question is looking for all numbers in a string.

#What I want:
'123mm' -> 123
'123mm1' -> 123

@Trimax well, no, its just msecs in my example as it's what I'm working with at the moment — Islarf, Aug 08 '16 at 09:36
Using RegEx is a way but isn't more pythonic; you must import the regex library. — Trimax, Aug 08 '16 at 09:36
@Chris_Rands Yeah, I have considered that, but I was trying to avoid it because it doesn't look very pythonic — Islarf, Aug 08 '16 at 09:36
I think using `split` is quite pythonic, you don't need the white space, just empty parentheses splits on all white space and newlines — Chris_Rands, Aug 08 '16 at 09:40
@PadraicCunningham yeah, in this case, because its trying to extract the number from the start of a measurement. It could also be used for currency if you keep the symbol at the end of the string — Islarf, Aug 08 '16 at 09:43
@Chris_Rands how could you use it if there is no space, '10mm', or '10.55€' — Islarf, Aug 08 '16 at 09:43
you can get the float by using the regex pattern `^(\d+(\.\d+)?)`, then you get int() if you need. — Trimax, Aug 08 '16 at 09:44
If you can have or integers or floats then you might be best off using a regex — Padraic Cunningham, Aug 08 '16 at 09:46
Possible duplicate of [Python: Extract numbers from a string](http://stackoverflow.com/questions/4289331/python-extract-numbers-from-a-string) — DocZerø, Aug 08 '16 at 09:46
@Kristof in a way, but with this i'm trying to not use regex. — Islarf, Aug 08 '16 at 09:47
@Islarf The answers to that question contain other techniques than just RE. — DocZerø, Aug 08 '16 at 09:49
@Kristof It's not an exact duplicate. as in this, I'm trying to duplicate the ability of parseInt(str) in Javascript. If I had the string ('123msecs2') I don't want the 2 at the end back. the Javascript parseInt, will just return 123. This other question wants to reap all numbers in a string. I'm trying to get only the numbers at the BEGINNING of a string. parseInt will return NaN on ('hi123hi') — Islarf, Aug 08 '16 at 09:55

score 1 · Accepted Answer · edited May 23 '17 at 12:14

1

If you have white space, use split:

>>> s = "123 msecs2"
>>> int(s.split()[0])
123

If you want to take the numbers from the start of a string only without white space (or using regex), try this:

>>> s = "123msecs2"
>>> int("".join(list(next(iter(())) if not x.isdigit() else x for x in s)))
123

Note, it takes inspiration from the discussion here about breaking out of list comprehensions.

edited May 23 '17 at 12:14

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answered Aug 08 '16 at 10:18

Chris_Rands

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If you add the original (val.split()[0]), including this I'll accept the answer – Islarf Aug 08 '16 at 12:33

bhansa · Answer 2 · 2016-08-08T09:47:26.330

-1

If var = '7 msecs'

By filter:

int(filter(str.isdigit, var))

By Regex:

import re
p = re.compile(ur'\d')
re.search(p, var)

Or By join:

s = ''.join(x for x in var if x.isdigit())
print int(s)
7

edited Aug 08 '16 at 09:47

answered Aug 08 '16 at 09:39

bhansa

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score -1 · Answer 3 · edited May 23 '17 at 12:08

-1

This is already answered here: Python: Extract numbers from a string

You could use a regular expression to extract all numbers from a string:

>>> import re
>>> s = "7 msecs"
>>> re.findall(r"\d+", s)
["7"]

If you only want the first number from the string as int, you could use:

>>> import re
>>> s = "7 msecs"
>>> int(re.findall(r"\d+", s)[0])
7

edited May 23 '17 at 12:08

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answered Aug 08 '16 at 09:42

pschill

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Karin · Answer 4 · 2016-08-08T09:53:29.713

If you want to avoid importing regex, you can try using isdigit(). But for what it's worth, I'd prefer int(var.split()[0]) to this:

var = '7 msecs'
numeric_end = 0
for i in xrange(len(var)):
    if not var[i].isdigit():
        numeric_end = i
        break

print int(var[:numeric_end])

I chose to track the index of the first non-digit character instead of building a string for slight memory/performance reasons. This also only extracts the first number in the string.

This will of course, only work for ints. For a float, you would have to also accept the . character (and probably keep track of whether or not you already have to determine if it's a valid float string).

Convert measurement from String to Int or Float

4 Answers4