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Hi,

I can't seem to find the right regular expression to achieve what I
want. I'd like to remove all characters from a string that are not
numbers, letters or underscores.

For example:

>>> magic_function('si_98%u^d@.as-*gf')
str: 'si_98udasgf'

Would you have any hint?

Thanks a lot!

Julien

On Jul 17, 10:13*am, Julien <jpha...@gmail.com> wrote:
> Hi,
>
> I can't seem to find the right regular expression to achieve what I
> want. I'd like to remove all characters from a string that are not
> numbers, letters or underscores.
>
> For example:
>
> >>> magic_function('si_98%u^d@.as-*gf')
>
> str: 'si_98udasgf'
>
> Would you have any hint?
>
> Thanks a lot!
>
> Julien

One quick and dirty way would be...

import string
safe_chars = string.ascii_letters + string.digits + '_'
test_string = 'si_98%u^d@.as-*gf'
''.join([char if char in safe_chars else '' for char in test_string])

you could also use a translation table, see string.translate (the
table it uses can be made with string.maketrans)

On Jul 17, 9:13*am, Julien <jpha...@gmail.com> wrote:
> Hi,
>
> I can't seem to find the right regular expression to achieve what I
> want. I'd like to remove all characters from a string that are not
> numbers, letters or underscores.
>
> For example:
>
> >>> magic_function('si_98%u^d@.as-*gf')
>
> str: 'si_98udasgf'

For speed, you can use 'string.translate', but simplest is to use a
comprehension:

import string

def magic_function(s, keep=string.ascii_letters + string.digits +
'_'):
return ''.join(c for c in s if c in keep)

--
Paul Hankin

Julien wrote:

> I can't seem to find the right regular expression to achieve what I
> want. I'd like to remove all characters from a string that are not
> numbers, letters or underscores.
>
> For example:
>
>>>> magic_function('si_98%u^d@.as-*gf')
> str: 'si_98udasgf'

the easiest way is to replace the things you don't want with an empty
string:

>>> re.sub("\W", "", "si_98%u^d@.as-*gf")
'si_98udasgf'

("\W" matches everything that is "not numbers, letters, or underscores",
where the alphabet defaults to ASCII. to include non-ASCII letters, add
"(?u)" in front of the expression, and pass in a Unicode string).

</F>