Implementation of Python data structure queues

Python queue

An Queue queue is a first-in, first-out (FIFO) data type. New elements are added to the end of Queue by joining the queue, which removes elements from the head of Queue.

Queue with lists:

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

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

def deQ():        #  define 1 Out of the team method 
  if len(queue) == 0:
    print "Cannot pop from an empty queue!"
  else:
    print 'Remove [', `queue.pop(0)`, ']'
    #  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 
    # queue.pop(0)  Always pop the first element in the queue 

def viewQ():      #  define 1 Method to display the contents of a queue 
    print queue

CMDs = {'u':enQ, 'o':deQ, 'v':viewQ}
#  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 = """
  (E)nqueue
  (D)equeue
  (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()

Queues and stacks are implemented in a similar way, except that the queue always pops the first element first and the stack always pops the last element first.

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