Python fragmentation knowledge (1): How to Use strip lstrip rstrip

I. Principles:

Strip in Python is used to remove the first and last characters of a string. Similarly, lstrip is used to remove the characters on the left, and rstrip is used to remove the characters on the right. All three functions can be passed in a parameter, specifying the first and last characters to be removed. It should be noted that the input is a character array. the compiler removes all the corresponding characters at both ends until no matching characters exist, such as: theString = 'saaaay yes no yaaaass 'print theString. strip ('put') theString is removed from the ['s ', 'A', 'y'] array until the characters are not in the array. Therefore, the output result is: yes no. The principle of lstrip and rstrip is the same. Note: When no parameters are input, spaces at the beginning and end are removed by default. TheString = 'saaaay yes no yaaaass 'print theString. strip ('put') print theString. strip ('put') # There is a space after 'put' print theString. lstrip ('put') print theString. rstrip ('put') running result: yes no es no yes no yaaaass saaaay yes no
Note: This explanation comes from :( pylemon's notebook): http://www.cnblogs.com/pylemon/archive/2011/05/18/2050179.html

Ii. Practical Application

Here is a demo used to control the output menu in pythonIED, select the corresponding options, and perform the corresponding operations. As follows:
Suppose there are two functions in the program: newUser and oldUser.

1 # Menu Control Interface 2 def showmenu (): 3 prompt = '''4*************************** 5 Welcome to Python System! 6 ----------------------- 7 | (N) ew User Login | 8 | (L) ogin your system | 9 | (Q) uit | 10 ----------------------- 11 Enter Choice: 12 ************************* 13 ''' 14 done = False15 while not done: 16 chosen = False17 while not chosen: 18 try: 19 choice = raw_input (prompt ). strip () [0]. lower () # Take the first character of the input string 20 Tb (EOFError, KeyboardInterrupt): 21 choice = 'q' # throw an exception 22 print '\ n You picked: [% s] '% choice23 if choice not in 'nlq': # determine whether the first character in the output string belongs to 'nlq' 24 print 'invalid option, tyr again '25 else: 26 chosen = True # Jump out of the loop if everything is normal 27 # control based on input information 28 if choice = 'q': done = True # if 'q' is input, the entire loop is exceeded, 29 if choice = 'N': newUser () # if 'n' is input, call the user registration function 30 if choice = 'l': oldUser () # if 'L' is entered, the user login function 31 32 is called. # main program 33 if _ name __= = "_ main _": 34 showmenu ()

Note: Pay attention to the red part of the code.