Is there an efficient way to strip out numbers from a string in python? Using nltk or base python?
Thanks, Ben
3 Answers
Yes, you can use a regular expression for this:
import re
output = re.sub(r'\d+', '', '123hello 456world')
print output # 'hello world'
3 Comments
ben890
This is perfect! Thanks Martin
Alex Huszagh
Can't go wrong with the regex solution, since it also translate very well to other instances (say he wants to remove letters next).
Kareem Khaleel
The best answer. Works like charm
str.translate should be efficient.
In [7]: 'hello467'.translate(None, '0123456789')
Out[7]: 'hello'
To compare str.translate against re.sub:
In [13]: %%timeit r=re.compile(r'\d')
output = r.sub('', my_str)
....:
100000 loops, best of 3: 5.46 µs per loop
In [16]: %%timeit pass
output = my_str.translate(None, '0123456789')
....:
1000000 loops, best of 3: 713 ns per loop
5 Comments
Jon Clements
The problem is:
str.translate is a bit difficult to make both 2.x/3.x compatible :(Jon Clements
So you'd need
my_str.translate({ord(ch): None for ch in '0123456789'}) in 3.x
Ross
I wonder how long r.sub() takes? Say, under conditions where you want to do this over multiple strings and you've pre-compiled the regex.
Robᵩ
@Ross - Judging from the code I put in my answer, 5.46µs.
Ross
@Rob - Ah right, I missed that the first line is the set up line. Looking at some best/worst cases translate seems to perform much better at worst case scenarios. Using 'python -m timeit' I came across the following in favour of translate;
'123hello 456world' - x5.0 '1234567890987654321012345678909876543210' - x17.0 '5a$%&^@)9lhk45g08j%Gmj3g09jSDGjg0034k' - x9.0 'hello world im your boss' - x 1.8Here's a method using str.join(), str.isnumeric(), and a generator expression which will work in 3.x:
>>> my_str = '123Hello, World!4567'
>>> output = ''.join(c for c in my_str if not c.isnumeric())
>>> print(output)
Hello, World!
>>>
This will also work in 2.x, if you use a unicode string:
>>> my_str = u'123Hello, World!4567'
>>> output = ''.join(c for c in my_str if not c.isnumeric())
>>> print(output)
Hello, World!
>>>
Hmm. Throw in a paperclip and we'd have an episode of MacGyver.
Update
I know that this has been closed out as a duplicate, but here's a method that works for both Python 2 and Python 3:
>>> my_str = '123Hello, World!4567'
>>> output = ''.join(map(lambda c: '' if c in '0123456789' else c, my_str))
>>> print(output)
Hello, World!
>>>
I have 3x as many dogs as 2 catsbe?