Strip out numbers from a string [closed]

Question

We have a bunch of strings for example: c1309, IF1306, v1309, p1209, a1309, mo1309.
In Python, what is the best way to strip out the numbers? All I need is: c, IF, v, p, a, mo from above example.

Answer 1

You can use regex:

>>> import re
>>> strs = "c1309, IF1306, v1309, p1209, a1309, mo1309"
>>> re.sub(r'\d','',strs)
'c, IF, v, p, a, mo'

or a faster version:

>>> re.sub(r'\d+','',strs)
'c, IF, v, p, a, mo'

timeit comparisons:

>>> strs = "c1309, IF1306, v1309, p1209, a1309, mo1309"*10**5

>>> %timeit re.sub(r'\d','',strs)
1 loops, best of 3: 1.23 s per loop

>>> %timeit re.sub(r'\d+','',strs)
1 loops, best of 3: 480 ms per loop

>>> %timeit ''.join([c for c in strs if not c.isdigit()])
1 loops, best of 3: 1.07 s per loop

#winner
>>> %timeit from string import digits;strs.translate(None, digits)
10 loops, best of 3: 20.4 ms per loop

Answer 2

>>> text = 'mo1309'
>>> ''.join([c for c in text if not c.isdigit()])
'mo'

This is faster than regex

python -m timeit -s "import re; text = 'mo1309'" "re.sub(r'\d','',text)"
100000 loops, best of 3: 3.99 usec per loop
python -m timeit -s "import re; text = 'mo1309'" "''.join([c for c in text if not c.isdigit()])"
1000000 loops, best of 3: 1.42 usec per loop
python -m timeit -s "from string import digits; text = 'mo1309'" "text.translate(None, digits)"
1000000 loops, best of 3: 0.42 usec per loop

but str.translate as suggested by @DavidSousa:

from string import digits
text.translate(None, digits)

is always the fastest in stripping characters.

Also itertools supplies a little known function called ifilterfalse

>>> from itertools import ifilterfalse
>>> ''.join(ifilterfalse(str.isdigit, text))
'mo'