在Python中，如何编写一个正则表达式来匹配以字符串a开始但不以B结束的字符串

Question

我有一些字符串，比如：

tool_abc
tool_abc_data
tool_xyz
tool_xyz_data
file_abc
file_xyz_data

我的目标是使用一个RegEx来匹配以tool_开始而不是以_data结束的所有字符串。我怎么写？

Answer 1

摘自https://docs.python.org/2/library/re.html#regular-expression-syntax:

(?<!...)
Matches if the current position in the string is not preceded by a match
for .... This is called a negative lookbehind assertion. Similar to positive 
lookbehind assertions, the contained pattern must only match strings of some
fixed length and shouldn’t contain group references. Patterns which start
with negative lookbehind assertions may match at the beginning of the string
being searched..

我认为您需要的regex是'^tool_.*$（？<！_data)':

>>> re.match('^tool_.*$(?<!_data)', 'tool_abc')
<_sre.SRE_Match object at 0x10ef4fd98>
>>> re.match('^tool_.*$(?<!_data)', 'tool_abc_data')
>>> re.match('^tool_.*$(?<!_data)', 'tool_abc_data_file')
<_sre.SRE_Match object at 0x10ef4fe00>
>>> re.match('^tool_.*$(?<!_data)', 'tool_abc_file')
<_sre.SRE_Match object at 0x10ef4fd98>
>>> re.match('^tool_.*$(?<!_data)', 'tool_abc_data')
>>> re.match('^tool_.*$(?<!_data)', 'abc_data')
>>> re.match('^tool_.*$(?<!_data)', 'file_xyz_data')
>>> re.match('^tool_.*$(?<!_data)', 'file_xyz')