Python中的正则表达式S2（搜索，匹配和查找全部）

Python中的正则表达式和示例|套装1
模块re提供对Python中正则表达式的支持。以下是此模块中的主要方法。
搜索模式的出现
re.search()：此方法返回None(如果模式不匹配), 或者返回re.MatchObject, 其中包含有关字符串匹配部分的信息。此方法在第一个匹配项后停止, 因此它最适合于测试正则表达式, 而不是提取数据。

# A Python program to demonstrate working of re.match(). import re# Lets use a regular expression to match a date string # in the form of Month name followed by day number regex = r "([a-zA-Z]+) (\d+)"match = re.search(regex, "I was born on June 24" )if match ! = None :# We reach here when the expression "([a-zA-Z]+) (\d+)" # matches the date string.# This will print [14, 21), since it matches at index 14 # and ends at 21. print "Match at index %s, %s" % (match.start(), match.end())# We us group() method to get all the matches and # captured groups. The groups contain the matched values. # In particular: #match.group(0) always returns the fully matched string #match.group(1) match.group(2), ... return the capture #groups in order from left to right in the input string #match.group() is equivalent to match.group(0)# So this will print "June 24" print "Full match: %s" % (match.group( 0 ))# So this will print "June" print "Month: %s" % (match.group( 1 ))# So this will print "24" print "Day: %s" % (match.group( 2 ))else : print "The regex pattern does not match."

输出：

Match at index 14, 21 Full match: June 24 Month: June Day: 24

【Python中的正则表达式S2（搜索，匹配和查找全部）】将模式与文本匹配
re.match()：此函数尝试将模式匹配到整个字符串。 re.match函数成功返回匹配对象, 失败则返回None。

re.match(pattern, string, flags=0)pattern : Regular expression to be matched. string : String where p attern is searched flags : We can specify different flags using bitwise OR (|).

# A Python program to demonstrate working # of re.match(). import re# a sample function that uses regular expressions # to find month and day of a date. def findMonthAndDate(string):regex = r "([a-zA-Z]+) (\d+)" match = re.match(regex, string)if match = = None : print "Not a valid date" returnprint "Given Data: %s" % (match.group()) print "Month: %s" % (match.group( 1 )) print "Day: %s" % (match.group( 2 ))# Driver Code findMonthAndDate( "Jun 24" ) print ("") findMonthAndDate( "I was born on June 24" )

查找所有出现的模式
re.findall()：以字符串列表形式返回字符串中所有不重复的模式匹配项。从左到右扫描字符串, 并以找到的顺序返回匹配项(来源：Python文档：https://docs.python.org/2/library/re.html)。

# A Python program to demonstrate working of # findall() import re# A sample text string where regular expression # is searched. string= """Hello my Number is 123456789 and my friend's number is 987654321"""# A sample regular expression to find digits. regex = '\d+'match = re.findall(regex, string) print (match)# This example is contributed by Ayush Saluja.

输出：

['123456789', '987654321']

正则表达式是一个巨大的话题。这是一个完整的图书馆。正则表达式可以做很多事情。你可以匹配, 搜索, 替换, 提取大量数据。例如, 下面的小代码非常强大, 可以从文本中提取电子邮件地址。因此, 我们可以使用easy.Lake regex查看python中的Web爬网程序和爬虫。

# extract all email addresses and add them into the resulting set new_emails = set(re.findall(r"[a-z0-9\.\-+_]+@[a-z0-9\.\-+_]+\.[a-z]+", text, re.I))

我们将很快讨论正则表达式的更多方法。
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首先, 你的面试准备可通过以下方式增强你的数据结构概念：Python DS课程。