How to map all numbers in a string to a list in Python? [duplicate]

Question

Say I have a string like

"There are LJFK$(#@$34)(,0,ksdjf apples in the (4,5)"

I want to be able to dynamically extract the numbers into a list: [34, 0, 4, 5].
Is there an easy way to do this in Python?

In other words,
Is there some way to extract contiguous numeric clusters separated by any delimiter?

If the string were "12.34", would you want [12, 34] or [12.34]? IOW, is it only contiguous-digit integers you want? — DSM
– DSM, Commented Apr 1, 2013 at 15:15
In this case it would be [12, 34], integers. The current answer works as desired (I just can't accept it yet) — John Smith
– John Smith, Commented Apr 1, 2013 at 15:18

phihag · Accepted Answer · 2013-04-01 15:09:25Z

7

Sure, use regular expressions:

>>> s = "There are LJFK$(#@$34)(,0,ksdjf apples in the (4,5)"
>>> import re
>>> list(map(int, re.findall(r'[0-9]+', s)))
[34, 0, 4, 5]

answered Apr 1, 2013 at 15:09

phihag

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7 Comments

Cairnarvon Over a year ago

Using a list comprehension is usually preferable to using map. Especially since you're just casting the result to a list anyway.

phihag Over a year ago

@Cairnarvon It usually is, except if you can simply call an existing function (because then you don't have to figure out the name of a temporary variable). The list creation is just for the nice output. If you were to iterate over the result, you could obviously skip it.

pradyunsg Over a year ago

You could have use \d+ for the regex too.

phihag Over a year ago

@Schoolboy Yes, but then one would have to use something significantly more complicated than int to support inputs like ٣٤.

pradyunsg Over a year ago

@phihag Why is that?? how will those inputs get through the filter??

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Kevin · Accepted Answer · 2013-04-01 15:22:53Z

2

You can also do this without regular expressions, although it requires some more work:

>>> s = "There are LJFK$(#@$34)(,0,ksdjf apples in the (4,5)"
>>> #replace nondigit characters with a space
... s = "".join(x if x.isdigit() else " " for x in s)
>>> print s
                   34   0                      4 5
>>> #get the separate digit strings
... digitStrings = s.split()
>>> print digitStrings
['34', '0', '4', '5']
>>> #convert strings to numbers
... numbers = map(int, digitStrings)
>>> print numbers
[34, 0, 4, 5]

answered Apr 1, 2013 at 15:22

Kevin

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2 Comments

DSM Over a year ago

I think I like this even better than the itertools.groupby solution I was going to propose.

John Smith Over a year ago

This is a great solution too

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