Python 正则表达 RegEx
导入模块
import re
简单 Python 匹配
# matching string
pattern1 = "cat"
pattern2 = "bird"
string = "dog runs to cat"
print(pattern1 in string)
print(pattern2 in string)
True
False
用正则寻找配对
# regular expression
pattern1 = "cat"
pattern2 = "bird"
string = "dog runs to cat"
print(re.search(pattern1, string))
print(re.search(pattern2, string))
<_sre.SRE_Match object; span=(12, 15), match='cat'>
None
匹配多种可能 使用 []
# multiple patterns ("run" or "ran")
ptn = r"r[au]n"
print(re.search(ptn, "dog runs to cat"))
<_sre.SRE_Match object; span=(4, 7), match='run'>
匹配更多种可能
# continue
print(re.search(r"r[A-Z]n", "dog runs to cat"))
print(re.search(r"r[a-z]n", "dog runs to cat"))
print(re.search(r"r[0-9]n", "dog r2ns to cat"))
print(re.search(r"r[0-9a-z]n", "dog runs to cat"))
None
<_sre.SRE_Match object; span=(4, 7), match='run'>
<_sre.SRE_Match object; span=(4, 7), match='r2n'>
<_sre.SRE_Match object; span=(4, 7), match='run'>
特殊种类匹配
数字
# \d : decimal digit
print(re.search(r"r\dn", "run r4n"))
# \D : any non-decimal digit
print(re.search(r"r\Dn", "run r4n"))
<_sre.SRE_Match object; span=(4, 7), match='r4n'>
<_sre.SRE_Match object; span=(0, 3), match='run'>
空白
# \s : any white space [\t\n\r\f\v]
print(re.search(r"r\sn", "r\nn r4n"))
# \S : opposite to \s, any non-white space
print(re.search(r"r\Sn", "r\nn r4n"))
<_sre.SRE_Match object; span=(0, 3), match='r\nn'>
<_sre.SRE_Match object; span=(4, 7), match='r4n'>
所有字母数字和”_”
# \w : [a-zA-Z0-9_]
print(re.search(r"r\wn", "r\nn r4n"))
# \W : opposite to \w
print(re.search(r"r\Wn", "r\nn r4n"))
<_sre.SRE_Match object; span=(4, 7), match='r4n'>
<_sre.SRE_Match object; span=(0, 3), match='r\nn'>
空白字符
# \b : empty string (only at the start or end of the word)
print(re.search(r"\bruns\b", "dog runs to cat"))
# \B : empty string (but not at the start or end of a word)
print(re.search(r"\B runs \B", "dog runs to cat"))
<_sre.SRE_Match object; span=(4, 8), match='runs'>
<_sre.SRE_Match object; span=(5, 11), match=' runs '>
特殊字符 任意字符
# \\ : match \
print(re.search(r"runs\\", "runs\ to me"))
# . : match anything (except \n)
print(re.search(r"r.n", "r[ns to me"))
<_sre.SRE_Match object; span=(0, 5), match='runs\\'>
<_sre.SRE_Match object; span=(0, 3), match='r[n'>
句尾句首
# ^ : match line beginning
print(re.search(r"^dog", "dog runs to cat"))
# $ : match line ending
print(re.search(r"cat$", "dog runs to cat"))
<_sre.SRE_Match object; span=(0, 3), match='dog'>
<_sre.SRE_Match object; span=(12, 15), match='cat'>
是否
# ? : may or may not occur
print(re.search(r"Mon(day)?", "Monday"))
print(re.search(r"Mon(day)?", "Mon"))
<_sre.SRE_Match object; span=(0, 6), match='Monday'>
<_sre.SRE_Match object; span=(0, 3), match='Mon'>
多行匹配
# multi-line
string = """
dog runs to cat.
I run to dog.
"""
print(re.search(r"^I", string))
print(re.search(r"^I", string, flags=re.M))
None
<_sre.SRE_Match object; span=(18, 19), match='I'>
0或多次
# * : occur 0 or more times
print(re.search(r"ab*", "a"))
print(re.search(r"ab*", "abbbbb"))
<_sre.SRE_Match object; span=(0, 1), match='a'>
<_sre.SRE_Match object; span=(0, 6), match='abbbbb'>
1或多次
# + : occur 1 or more times
print(re.search(r"ab+", "a"))
print(re.search(r"ab+", "abbbbb"))
None
<_sre.SRE_Match object; span=(0, 6), match='abbbbb'>
可选次数
# {n, m} : occur n to m times
print(re.search(r"ab{2,10}", "a"))
print(re.search(r"ab{2,10}", "abbbbb"))
None
<_sre.SRE_Match object; span=(0, 6), match='abbbbb'>
group 组
# group
match = re.search(r"(\d+), Date: (.+)", "ID: 021523, Date: Feb/12/2017")
print(match.group())
print(match.group(1))
print(match.group(2))
021523, Date: Feb/12/2017
021523
Feb/12/2017
match = re.search(r"(?P<id>\d+), Date: (?P<date>.+)", "ID: 021523, Date: Feb/12/2017")
print(match.group('id'))
print(match.group('date'))
021523
Feb/12/2017
寻找所有匹配
# findall
print(re.findall(r"r[ua]n", "run ran ren"))
['run', 'ran']
# | : or
print(re.findall(r"(run|ran)", "run ran ren"))
['run', 'ran']
替换
# re.sub() replace
print(re.sub(r"r[au]ns", "catches", "dog runs to cat"))
dog catches to cat
分裂
# re.split()
print(re.split(r"[,;\.]", "a;b,c.d;e"))
['a', 'b', 'c', 'd', 'e']
compile
# compile
compiled_re = re.compile(r"r[ua]n")
print(compiled_re.search("dog ran to cat"))
<_sre.SRE_Match object; span=(4, 7), match='ran'>
