import re
subject = """These concepts are represented by simple Python classes.  
Edit the polls/models.py file so it looks like this: 

[code]  
from django.db import models

class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published') 
[/code]"""

regex = re.compile(r'(?s)\[code\].*?\[/code\]|(\n)')
def myreplacement(m):
    if m.group(1):
        return "<br />"
    else:
        return m.group(0)
replaced = regex.sub(myreplacement, subject)
print(replaced)