import re
def regexp():
s = '<html><head><title>Title</title>'
# with pre compiled pattern
pattern = re.compile('title')
match = pattern.search(s)
#check for existence
print match
# >> <_sre.SRE_Match object at 0x011E0E58> #loop through all matches
match = pattern.findall(s)
print match
# >> ['title', 'title'] #grouping matches
s = '<html><head><title>Title</title>'
pattern = re.compile('(head).*(title)')
match = pattern.search(s)
print match.group(0)
# >>head><title>Title</title
print match.group(1)
# >>head #replace
pattern = re.compile('title')
print pattern.sub("ersetzt",s)
# >> <html><head><ersetzt>Title</ersetzt> #split
pattern = re.compile('title')
print pattern.split(s)
# >> ['<html><head><', '>Title</', '>'] #replace alle lines in file by "eineZeile"
f = open('test.txt','r')
l= ['eineZeile' for l in f.readlines()]
f.close()
print l
f=open("test.txt", "w")
f.writelines(l)
f.close()
regexp()