The python regular expression determines whether the string is all lowercase examples _python

Copy Code code as follows:

#-*-coding:cp936-*-
Import re
S1 = ' ADKKDK '
S2 = ' ABC123EFG '

an = Re.search (' ^[a-z]+$ ', S1)
If an:
print ' S1: ', An.group (), ' all lowercase '
Else
Print S1, "Not all lowercase!" "

an = Re.match (' [a-z]+$ ', S2)
If an:
print ' s2: ', An.group (), ' all lowercase '
Else
Print S2, "Not all lowercase!" "

1. Regular expressions are not part of Python and need to be referenced by the RE module

2. The matching form is: Re.search (regular expression, with matching string) or re.match (regular expression, with matching string). The difference is that the latter default begins with the start character (^). So

Re.search (' ^[a-z]+$ ', S1) is equivalent to Re.match (' [a-z]+$ ', S2 ')
3. If the match fails, an = Re.search (' ^[a-z]+$ ', S1) returns none

Group is used to group matching results

Copy Code code as follows:

Import re
A = "123abc456"
Print Re.search ([0-9]*) ([a-z]*) ([0-9]*), a). Group (0) #123abc456, return to the whole
Print Re.search ([0-9]*) ([a-z]*) ([0-9]*), a). Group (1) #123
Print Re.search ([0-9]*) ([a-z]*) ([0-9]*), a). Group (2) #abc
Print Re.search ([0-9]*) ([a-z]*) ([0-9]*), a). Group (3) #456

1 The three sets of parentheses in the regular expression divide the result into three groups

Group () is the same group (0) that matches the overall result of the regular expression

Group (1) lists the first bracket matching part, Group (2) lists the second bracket matching part, and group (3) lists the third bracket matching part.

2) No match succeeded, Re.search () returns none

3 of course Zheng is the expression of no parentheses, group (1) certainly wrong.