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简单的正则表达式python实现

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简单的Python实现正则表达式，对文字的分析用的多，爬虫也会用到。

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import re
str = 'dog cat dog'
r_str = r'dog'
match = re.match(r_str,str)
print match.group(0)
#dog
match = re.search(r_str,str)
print match.group(0)
#dog
print match.start()
#0
print match.end()
#3
List = re.findall(r_str,str)
print List
#['dog', 'dog']
contactInfo = 'Doe, John: 555-1212'
r_str = r'\w+, \w+: \S+'
match = re.search(r_str,contactInfo)
print match.group(0)
#Doe, John: 555-1212
r_group_str = r'(\w+), (\w+): (\S+)'
match = re.search(r_group_str,contactInfo)
print match.group(0)
#Doe, John: 555-1212
print match.group(1)
#Doe
print match.group(2)
#John
print match.group(3)
#555-1212
r_group_name_str = r'(?P<last>\w+), (?P<first>\w+): (?P<phone>\S+)'
match = re.search(r_group_name_str,contactInfo)
print match.group('last')
#Doe
print match.group('first')
#John
print match.group('phone')
#555-1212
List = re.findall(r_group_str,contactInfo)
print List
#[('Doe', 'John', '555-1212')]