Python Challenge level 3

http://www.pythonchallenge.com/pc/def/equality.html

- See also: https://docs.python.org/2/library/re.html
- As the previous level, copy the mess message in the page source
- Try to find " 3 uppercase + 1 lowercase + 3 uppercase" pattern
  - For example, "AAAaAAA"
  - They emphasize "EXACTLY 3 bodyguards," so string like "AAAAaAAA" is not acceptable
- Finally, concat all lowercase letters

import re
f = open("filename.txt", 'r')
pattern = re.compile('[^A-Z][A-Z]{3}([a-z])[A-Z]{3}[^A-Z]')  
ans = ''
for line in f:
 result = re.findall(pattern, line)
 ans = ans + ''.join(result)
print ans
f.close()

- The answer is "linkedlist"