Removing all non-numeric characters from string in Python

How do we remove all non-numeric characters from a string in Python?

>>> import re
>>> re.sub("[^0-9]", "", "sdkjh987978asd098as0980a98sd")
'987978098098098'

Not sure if this is the most efficient way, but:

>>> ''.join(c for c in "abc123def456" if c.isdigit())
'123456'

The ''.join part means to combine all the resulting characters together without any characters in between. Then the rest of it is a list comprehension, where (as you can probably guess) we only take the parts of the string that match the condition isdigit.

This should work for both strings and unicode objects in Python2, and both strings and bytes in Python3:

# python <3.0
def only_numerics(seq):
    return filter(type(seq).isdigit, seq)

# python ≥3.0
def only_numerics(seq):
    seq_type= type(seq)
    return seq_type().join(filter(seq_type.isdigit, seq))

@Ned Batchelder and @newacct provided the right answer, but ...

Just in case if you have comma(,) decimal(.) in your string:

import re
re.sub("[^\d\.]", "", "$1,999,888.77")
'1999888.77'