string对象方法

一：str.isalnum() ，str.isalpha()，str.isdigit() ，str.islower() ，str.isupper() 

1.str.isalnum() 
This method checks if all the characters of a string are alphanumeric (a-z, A-Z and 0-9).

>>> print 'ab123'.isalnum()
True
>>> print 'ab123#'.isalnum()
False

2.str.isalpha() 
This method checks if all the characters of a string are alphabetical (a-z and A-Z).

>>> print 'abcD'.isalpha()
True
>>> print 'abcd1'.isalpha()
False

3.str.isdigit() 
This method checks if all the characters of a string are digits (0-9).

>>> print '1234'.isdigit()
True
>>> print '123edsd'.isdigit()
False

4.str.islower() 
This method checks if all the characters of a string are lowercase characters (a-z)

>>> print 'abcd123#'.islower()
True
>>> print 'Abcd123#'.islower()
False

5.str.isupper() 　

This method checks if all the characters of a string are uppercase characters (A-Z).　

>>> print 'ABCD123#'.isupper()
True
>>> print 'Abcd123#'.isupper()
False