python while 循環 if 循環

Python 編程中 while 語句用於循環執行程序，即在某條件下，循環執行某段程序，以處理需要重複處理的相同任務。其基本形式爲：

執行語句可以是單個語句或語句塊。判斷條件可以是任何表達式，任何非零、或非空（null）的值均爲true。當判斷條件假false時，循環結束。

執行流程圖如下：

• if else 的兩種循環結構

name = 'python'
flag = True


if name == 'luna':
    print flag
else:
    print name


if name == 'xiaphong':
    print flag
elif name == 'xiapong':
    print flag
elif name == 'python':
    print '朋友你猜對了'
else:
    print False

• while 循環：

#!/usr/bin/python

count = 0
while count < 100:
    print 'The count is:', count
    count = count + 1

print "Good bye!"

• 無限循環：

#!/usr/bin/python
# -*- coding: UTF-8 -*-
 
var = 1
while var == 1 :  # 該條件永遠爲true，循環將無限執行下去
   num = raw_input("Enter a number :")
   print "You entered: ", num
 
print "Good bye!"

輸出：

Python 2.7.15 |Anaconda, Inc.| (default, Dec 10 2018, 21:57:18) [MSC v.1500 64 bit (AMD64)]
Type "copyright", "credits" or "license" for more information.
IPython 5.8.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.
PyDev console: using IPython 5.8.0
Python 2.7.15 |Anaconda, Inc.| (default, Dec 10 2018, 21:57:18) [MSC v.1500 64 bit (AMD64)] on win32
runfile('D:/pycharm/TEST02/python file/test02.py', wdir='D:/pycharm/TEST02/python file')
Enter a number  :>? 3
You entered: 傻瓜 3
Enter a number  :