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