python中字符串比较使用is、==和cmp()总结

 The operators ``is`` and ``is not`` test for object identity: ``x is y`` is true if and only if *x* and *y* are the same object. ``x is not y`` yields the inverse truth value. cmp(...) cmp(x, y) -> integer Return negative if xy.

 >>> a = 256 >>> b = 256 >>> id(a) 9987148 >>> id(b) 9987148 >>> a = 257 >>> b = 257 >>> id(a) 11662816 >>> id(b) 11662828 

 #!/usr/bin/python strtmp = '192.169.1.161' file_object = open(r'public_ip.txt') try: all_the_text = file_object.readlines() firstline = all_the_text[0].rstrip() finally: file_object.close() #print firstline #if strtmp == firstline: s = (strtmp is firstline) print s if (strtmp is firstline): print 'yes' else: print 'no' 

 #-*-conding:utf-8-*- i='xinwen'; m=input(); if i==m: print('yes'); else: print('no'); input(); 

 #!/usr/bin/python # Filename: if.py number = 23 guess = int(raw_input('Enter an integer : ')) if guess == number: print 'Congratulations, you guessed it.' # New block starts here print "(but you do not win any prizes!)" # New block ends here elif guess  number to reach here print 'Done' # This last statement is always executed, after the if statement is executed 

 >>> x='a' >>> x+'b' is 'ab' False >>> x+'b' == 'ab' True >>> cmp(x+'b','ab') 0 >>> id(x+'b') 32468384L >>> id('ab') 46933696L >>> 

 >>> a='abc' >>> b='abc' >>> a is b True >>> id(a) == id(b) True >>>