Python regex not to match http://

One solution I can think of is to form a combined pattern for HTTP-URLs and your pattern, then filter the matches accordingly:

import re

t = "http://www.egg1.com http://egg2.com egg3 egg4"

p = re.compile('(http://\S+)|(egg\d)')
for url, egg in p.findall(t):
  if egg:
    print egg

prints:

egg3
egg4

---

UPDATE: To use this idiom with re.sub(), just supply a filter function:

p = re.compile(r'(http://\S+)|(egg(\d+))')

def repl(match):
    if match.group(2):
        return 'spam{0}'.format(match.group(3))
    return match.group(0)

print p.sub(repl, t)

prints:

http://www.egg1.com http://egg2.com spam3 spam4

This will not capture http://...:

(?:http://.*?\s+)|(egg1)