Python正则表达式：在多行上匹配字符？

我在pythonchallenge.com上做挑战，我在使用通用正则表达式时遇到了麻烦

例如，如果我们有以下文本：

hello world
<!--
%%$@_$^__#)^)&!_+]!*@&^}@[@%]()%+$&[(_@%+%$*^@$^!+]!&_#)_*}{}}!}_]$[%}@[{_@#_^{*
@##&{#&{&)*%(]{{([*}@[@&]+!!*{)!}{%+{))])[!^})+)$]#{*+^((@^@}$[*a*$&^{$!@#$%)!@(&bc  

但是，我对正则表达式有问题。我正在regex tester上测试它，但它似乎并没有达到我想要的效果

这是我的正则表达式

<!--[a-z]*

>>导入re
>>>打印strs=“”你好，世界
重新导入
苏=''你好，世界
xxxx你好，世界yyyy
"
<!--[a-z]*

>>> import re
>>> print strs = """hello world
<!--
%%$@_$^__#)^)&!_+]!*@&^}@[@%]()%+$&[(_@%+%$*^@$^!+]!&_#)_*}{}}!}_]$[%}@[{_@#_^{*
@##&{#&{&)*%(]{{([*}@[@&]+!!*{)!}{%+{))])[!^})+)$]#{*+^((@^@}$[*a*$&^{$!@#$%)!@(&bc"""
>>> re.findall(r'[a-zA-Z]+',strs.split('<!--')[-1])
['a', 'bc']

import re

su = '''hello world
xxxx hello world yyyy
<!--
_+]!yuyu*@&^}@?!hello world[@%]^@}$[*a*$&^!@(&bc??,=hello'''

print su

pat = '([a-z]+)(?![a-z])(?<!world)'
print "\nexcluding all the words 'world'\n%s" % pat
print re.findall(pat,su)

pat = '([a-z]+)(?![a-z])(?<!\Ahello world)'
print "\nexcluding the word 'world' of the starting string 'hello world'\n%s" % pat
print re.findall(pat,su)

pat = '([a-z]+)(?![a-z])(?<!hello world)'
print "\nexcluding all the words 'world' of a string 'hello world'\n%s" % pat
print re.findall(pat,su)

print '\n-----------'

pat = '([a-z]+)(?![a-z])(?<!hello)'
print "\nexcluding all the words 'hello'\n%s" % pat
print re.findall(pat,su)

pat = '([a-z]+)(?![a-z])(?<!\Ahello)'
print "\nexcluding the starting word 'hello'\n%s" % pat
print re.findall(pat,su)

pat = '([a-z]+)(?![a-z])(?<!hello(?= world))'
print "\nexcluding all the words 'hello' of a string 'hello world'\n%s" % pat
print re.findall(pat,su)

print '\n-----------'

pat = '([a-z]+)(?![a-z])(?<!hello|world)'
print "\nexcluding all the words 'hello' and 'world'\n%s" % pat
print re.findall(pat,su)

pat = '([a-z]+)(?![a-z])(?<!hello(?= world))(?<!hello world)'
print "\nexcluding all the words of a string 'hello world'\n%s" % pat
print re.findall(pat,su)

pat = '([a-z]+)(?![a-z])(?<!\Ahello(?= world))(?<!\Ahello world)'
print "\nexcluding all the words of the starting string 'hello world'\n%s" % pat
print re.findall(pat,su)

hello world
xxxx hello world yyyy
<!--
_+]!yuyu*@&^}@?!hello world[@%]^@}$[*a*$&^!@(&bc??,=hello

excluding all the words 'world'
([a-z]+)(?![a-z])(?<!world)
['hello', 'xxxx', 'hello', 'yyyy', 'yuyu', 'hello', 'a', 'bc', 'hello']

excluding the word 'world' of the starting string 'hello world'
([a-z]+)(?![a-z])(?<!\Ahello world)
['hello', 'xxxx', 'hello', 'world', 'yyyy', 'yuyu', 'hello', 'world', 'a', 'bc', 'hello']

excluding all the words 'world' of a string 'hello world'
([a-z]+)(?![a-z])(?<!hello world)
['hello', 'xxxx', 'hello', 'yyyy', 'yuyu', 'hello', 'a', 'bc', 'hello']

-----------

excluding all the words 'hello'
([a-z]+)(?![a-z])(?<!hello)
['world', 'xxxx', 'world', 'yyyy', 'yuyu', 'world', 'a', 'bc']

excluding the starting word 'hello'
([a-z]+)(?![a-z])(?<!\Ahello)
['world', 'xxxx', 'hello', 'world', 'yyyy', 'yuyu', 'hello', 'world', 'a', 'bc', 'hello']

excluding all the words 'hello' of a string 'hello world'
([a-z]+)(?![a-z])(?<!hello(?= world))
['world', 'xxxx', 'world', 'yyyy', 'yuyu', 'world', 'a', 'bc', 'hello']

-----------

excluding all the words 'hello' and 'world'
([a-z]+)(?![a-z])(?<!hello|world)
['xxxx', 'yyyy', 'yuyu', 'a', 'bc']

excluding all the words of a string 'hello world'
([a-z]+)(?![a-z])(?<!hello(?= world))(?<!hello world)
['xxxx', 'yyyy', 'yuyu', 'a', 'bc', 'hello']

excluding all the words of the starting string 'hello world'
([a-z]+)(?![a-z])(?<!\Ahello(?= world))(?<!\Ahello world)
['xxxx', 'hello', 'world', 'yyyy', 'yuyu', 'hello', 'world', 'a', 'bc', 'hello']

print su

print "\ncatching all the lettered strings after <!--"
print "re.compile('^.+?<!--|([a-z]+)',re.DOTALL)"
rgx = re.compile('^.+?<!--|([a-z]+)',re.DOTALL)
print [x.group(1) for x in rgx.finditer(su) if x.group(1)]

print ("\ncatching all the lettered strings after <!--\n"
       "excluding all the words 'world'")
print "re.compile('^.+?<!--|([a-z]+)(?<!world)',re.DOTALL)"
rgx = re.compile('^.+?<!--|([a-z]+)(?![a-z])(?<!world)',re.DOTALL)
print [x.group(1) for x in rgx.finditer(su) if x.group(1)]

print ("\ncatching all the lettered strings after <!--\n"
       "excluding all the words 'hello'")
print "re.compile('^.+?<!--|([a-z]+)(?<!hello)',re.DOTALL)"
rgx = re.compile('^.+?<!--|([a-z]+)(?![a-z])(?<!hello)',re.DOTALL)
print [x.group(1) for x in rgx.finditer(su) if x.group(1)]

print ("\ncatching all the lettered strings after <!--\n"
       "excluding all the words 'hello' belonging to a string 'hello world'")
print "re.compile('^.+?<!--|([a-z]+)(?<!hello(?= world))',re.DOTALL)"
rgx = re.compile('^.+?<!--|([a-z]+)(?![a-z])(?<!hello(?= world))',re.DOTALL)
print [x.group(1) for x in rgx.finditer(su) if x.group(1)]

hello world
xxxx hello world yyyy
<!--
_+]!yuyu*@&^}@?!hello world[@%]^@}$[*a*$& <!-- ^!@(&bc??,=hello

catching all the lettered strings after first <!--
re.compile('.+?<!--|([a-z]+)',re.DOTALL)
['yuyu', 'hello', 'world', 'a', 'bc', 'hello']

catching all the lettered strings after first <!--
excluding all the words 'world'
re.compile('.+?<!--|([a-z]+)(?<!world)',re.DOTALL)
['yuyu', 'hello', 'a', 'bc', 'hello']

catching all the lettered strings after first <!--
excluding all the words 'hello'
re.compile('.+?<!--|([a-z]+)(?<!hello)',re.DOTALL)
['yuyu', 'world', 'a', 'bc']

catching all the lettered strings after first <!--
excluding all the words 'hello' belonging to a string 'hello world'
re.compile('.+?<!--|([a-z]+)(?<!hello(?= world))',re.DOTALL)
['yuyu', 'world', 'a', 'bc', 'hello']