Python While Loop Statement

In Python programming, the while statement is used to execute a program in a loop, that is to say, under certain conditions, a program is executed in a loop to deal with the same tasks that need to be processed repeatedly. Its basic form is:

The while judgment condition:
    Execution statement...

Execution statements can be a single statement or block of statements. The judgment condition can be any expression, and any non-zero or null value is true.

When the condition false false false is judged, the loop ends.

The execution flow chart is as follows:

Gif demonstrates the Python while statement execution process

The above code executes the output:

The count is: 0
The count is: 1
The count is: 2
The count is: 3
The count is: 4
The count is: 5
The count is: 6
The count is: 7
The count is: 8
Good bye!

There are two other important commands in the while statement: continue, break to skip the loop, continue to skip the loop, break to exit the loop, and "judgment condition" can also be a constant, which means that the loop must hold. The specific usage is as follows:

Infinite cycle

If the conditional judgement statement is always true, the loop will continue indefinitely, as shown in the following example:

The output of the above example is as follows:

Enter a number  :20
You entered:  20
Enter a number  :29
You entered:  29
Enter a number  :3
You entered:  3
Enter a number between :Traceback (most recent call last):
  File "test.py", line 5, in <module>
    num = raw_input("Enter a number :")
KeyboardInterrupt

Note: The above infinite loops can be interrupted by CTRL+C.

Cyclic use of else statements

In python, while... Else executes an else statement block when the loop condition is false:

The output of the above example is as follows:

0 is less than 5
1 is less than 5
2 is less than 5
3 is less than 5
4 is less than 5
5 is not less than 5

Simple statement group

Similar to the syntax of if statements, if you have only one statement in your while loop, you can write that statement on the same line as while, as follows:

Note: The above infinite loops can be interrupted by CTRL+C.

Classic Comments:

1. #!/usr/bin/python
   # -*- coding: UTF-8 -*-
   
   import random
   s = int(random.uniform(1,10))
   #print(s)
   m = int(input('Input integer:'))
   while m != s:
   	if m > s:
   		print('Big')
   		m = int(input('Input integer:'))
   	if m < s:
   		print('Small')
   		m = int(input('Input integer:'))
   	if m == s:
   		print('OK')
   		break;

   I'm a lovely boy. Sleeping is the best man in the world.

   I'm a lovely boy, sleeping is the world's man

     col***iansy@Outlook.com

   Four months ago (04-18)

2. June

     438***@qq.com

   Guess boxing games

   #!/usr/bin/python
   # -*- coding: UTF-8 -*-
   
   import random
   while 1:
       s = int(random.randint(1, 3))
       if s == 1:
           ind = "stone"
       elif s == 2:
           ind = "Scissors"
       elif s == 3:
           ind = "cloth"
       m = raw_input('Input stones, scissors, cloth,input"end"End the game:')
       blist = ['stone', "Scissors", "cloth"]
       if (m not in blist) and (m != 'end'):
           print "Input error, please re-enter!"
       elif (m not in blist) and (m == 'end'):
           print "\n Game Exit..."
           break
       elif m == ind :
           print "The computer is out: " + ind + "，It ends in a draw!"
       elif (m == 'stone' and ind =='Scissors') or (m == 'Scissors' and ind =='cloth') or (m == 'cloth' and ind =='stone'):
           print "The computer is out: " + ind +"，You win!"
       elif (m == 'stone' and ind =='cloth') or (m == 'Scissors' and ind =='stone') or (m == 'cloth' and ind =='Scissors'):
           print "The computer is out: " + ind +"，You lost!"

   Test results:

   Input stone, scissors, cloth, enter "end" to end the game: stone
    Computer out: Stone, draw!
   Input stone, scissors, cloth, enter "end" to end the game: stone    
   The computer is out: scissors, you win!
   Enter stone, scissors and cloth, and enter "end" to end the game:

   June

   June

     438***@qq.com

   Three months ago (04-27)

3. Sunset Morning Injury

     112***5110@qq.com

   Shake the Sieve Game

   #!/usr/bin/env python3
   # -*- coding: utf-8 -*-
   
   import random
   import sys
   import time
   
   result = []
   while True:
       result.append(int(random.uniform(1,7)))
       result.append(int(random.uniform(1,7)))
       result.append(int(random.uniform(1,7)))
       print result
       count = 0
       index = 2
       pointStr = ""
       while index >= 0:
           currPoint = result[index]
           count += currPoint
           index -= 1
           pointStr += " "
           pointStr += str(currPoint)
       if count <= 11:
           sys.stdout.write(pointStr + " -> " + "Small" + "\n")
           time.sleep( 1 )   # Sleep for a second
       else:
           sys.stdout.write(pointStr + " -> " + "large" + "\n")
           time.sleep( 1 )   # Sleep for a second
       result = []

   Sunset Morning Injury

   Sunset Morning Injury

     112***5110@qq.com

   Three months ago (05-03)

4.    (+__+)

     lk0***21428@126.com

   Decimal to binary

   #!/usr/bin/python
   # -*- coding: UTF-8 -*-
   
   denum = input("Input decimal number:")
   print denum,"(10)",
   binnum = []
   # Binary Number
   while denum > 0:
       binnum.append(str(denum % 2)) # Stack pressing
       denum //= 2
   print '= ',
   while len(binnum)>0:
       import sys
       sys.stdout.write(binnum.pop()) # No space output print'(2)'