Replacing “<” with “*” with a Python regex

Question

I need to go through strings in a list "listb", replacing the character "<" with "*".

I tried like this:

import re
for i in listb:
    i = re.sub('\<','\*', 0)

But I keep getting TypeError: expected string or buffer.

Not sure what am I doing wrong and examples on the net were not much help.

Answer 1

See the docs

As per Seth's comment, the best way to do this using regular expressions is going to be:

listb = [re.sub(r'<',r'*', i) for i in listb]

As @Paco, said, you should be using str.replace() instead. But if you still want to use re:

You're putting 0 where the string is supposed to go! The TypeError is from the that third parameter. It's an int, needs to be a string.

Side note: always use raw strings, denoted by r'' , in your regexes, so you don't have to escape.

>>> listb = ['abc', '<asd*', '<<>>**']
>>> for i in listb:
...     i = re.sub(r'<',r'*', i)
...     print i
... 
abc
*asd*
**>>**
>>> listb
['abc', '<asd*', '<<>>**']

if you want a new list with all those replaced, do:

>>> listx = []
>>> for i in listb:
...     listx.append(re.sub(r'<',r'*', i))
... 
>>> listx
['abc', '*asd*', '**>>**']
>>> listb
['abc', '<asd*', '<<>>**']
>>> listb = listx

If you really don't want to create a new list, you can iterate through the indices.

Note that you're not changing i in the list. I would create a new list here. Each i here is its own variable, which doesn't point to listb.

Answer 2

>>> my_string = 'fowiejf<woiefjweF<woeiufjweofj'
>>> my_string.replace('<', '*')
'fowiejf*woiefjweF*woeiufjweofj'

Why are you using the re module for such a simple thing? you can use the .replace method.