Python data structure stack instance code

Python stack

The stack is a last in, first out (LIFO) data structure that can be used to handle most flows of programs with a last in, first out nature.
In the stack, push and pop are common terms:

push: means to push an object onto a stack. pop: means to push an object out of a stack.

Here is a simple stack structure implemented by Python:

stack = []         #  Initialize the 1 List data type objects ,  As a 1 A stack 

def pushit():       #  define 1 A push method 
  stack.append(raw_input('Enter New String: ').strip())   
  #  prompt 1 A stack  String  object ,  call  Str.strip()  Guaranteed input  String  The value does not contain extra Spaces 

def popit():        #  define 1 A stack method 
  if len(stack) == 0:
    print "Cannot pop from an empty stack!"
  else:
    print 'Remove [', `stack.pop()`, ']'
    #  Use inverted single quotes (` `) To take the place of  repr(),  the  String  Is enclosed in quotation marks ,  Instead of just showing  String  The value of the 

def viewstack():      #  define 1 Method to display the contents of the stack 
    print stack

CMDs = {'u':pushit, 'o':popit, 'v':viewstack}
#  define 1 a  Dict  Type of object ,  Map the character to the corresponding  function . You can do this by entering characters 

def showmenu():      #  define 1 Action menu prompt method 
  pr = """
  p(U)sh
  p(O)p
  (V)iew
  (Q)uit

  Enter choice: """

  while True:
    while True:
      try:
        choice = raw_input(pr).strip()[0].lower()
        # Str.strip()  Get rid of  String  Extra space before and after the object 
        # Str.lower()  Converts multiple inputs to lowercase ,  It is convenient for the later unification 1 judge 
        #  The input  ^D(EOF,  produce 1 a  EOFError  abnormal )
        #  The input  ^C( Break out ,  produce 1 a  keyboardInterrupt  abnormal )

      except (EOFError, KeyboardInterrupt, IndexError):
        choice = 'q'

      print '\nYou picked: [%s]' % choice

      if choice not in 'uovq':
        print 'Invalid option, try again'
      else:
        break


    if choice == 'q':
      break
    CMDs[choice]()
    #  To obtain  Dict  Corresponding to the Chinese character  functionName,  Implement function calls 

if __name__ == '__main__':
  showmenu()

NOTE: in the stack data structure, List data type object container and variable features are mainly applied. List.append () and List.pop () are two list types with built-in function calls.

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