Python replace using regex

Question

Does anyone know how to replace all ocurences of '<\d+' regex with '\r\n<\d+', for example

"<20"

should be transformed to

"\r\n<20"

but

"> HELLO < asassdsa"

shuld be untouched

codaddict · Accepted Answer · 2012-02-08 11:31:06Z

10

>>> import re
>>> str = "<20"
>>> output = re.sub(r'<(?=\d)', r'\r\n<', str)
>>> output
'\r\n<20'

answered Feb 8, 2012 at 11:31

codaddict

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2 Comments

Why not go all the way and put the entire regex into the lookahead?

@Tim: That's what I thought. Also, maybe we shouldn't encourage the use of str as a variable name, although I always fail to find a better name :(

Niklas B. · Accepted Answer · 2012-02-08 11:50:33Z

3

import re
def replace(value):
  return re.sub(r'(<\d)', r'\r\n\1', value)

Or using lookahead:

import re
def replace(value):
  return re.sub(r'(?=<\d)', r'\r\n', value)

answered Feb 8, 2012 at 11:30

Niklas B.

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