[Python]几个正则表达式匹配的例子

例一、匹配以abc开头的单词。

text = "abcthis is thatabc colvin"
pat = r"\b(?=abc)\w*"
print re.findall(pat,text)

>>>

['abcthis']

例二、匹配不是以abc开头的单词。

text = "abcthis is thatabc colvin"
pat2 = r"\b(?!abc)\w+"
print re.findall(pat2,text)

>>>

['is', 'thatabc', 'colvin']

text = "abcthis is thatabc colvin"
pat3 = r"(?<!\w)(?=\w)(?!abc)\w+"
print re.findall(pat3,text)

>>>

['is', 'thatabc', 'colvin']

print re.findall(r"\b[^\Wa][^\Wb]?[^\Wc]?\w*\b","abcthis is abcthat colvin")

>>>

['is', 'colvin']

def getpat(str):
    pat = r"".join(["[^\W"+y+"]"+"?"*(x>0) for x,y in enumerate(str)])
    pat = r"\b"+pat+r"\w*\b"
    return pat

pat = getpat("abc")
print re.findall(pat,text)

>>>

['is', 'thatabc', 'colvin']

例三、匹配不包含abc的单词。

text = "abcthis is thatabc colvin"
pat4 = r"\b(((?!abc)\w)+)\b"
print re.findall(pat4,text)

>>>

[('is', 's'), ('colvin', 'n')]

例四、对字符串中的数值每3位添加一个小数点：

13324323  =>  13.324.323  

This is 1965th    =>  This is 1965th

333   =>  333

print re.sub(r'(?<=\d)(?=(\d\d\d)+\b)', '.', str('435453454534'))

>>>

435.453.454.534