Chapter II Python control statements

Chapter II Control statements

A. IF conditional statement

　　1. Basic if conditional statement　

　if condition:
    　　　　code block
    　　　　code block
　　　　else:
    　　　　code block

　　2. Conditions nested if statements

if condition:
    if condition:
        code block
        code block
    else:
        code block
else:
    code block
    code block

　　3. elif multiple conditional statements

if condition:
    code block
    code block
elif condition:
    code block
    code block
elif condition
    code block
    code block
else:
    code block 

　　4. if multiple conditional statements pass usage

if condition:
    pass
else:
    code block
print("xxxxxx")

Two, while loop

　　1 dead loop code

 

import time
while a == a:
    print("ok",time.time())

 

　　2. ordinary cycle

--------------------------------------------------------

count = 0
while count < 20:
    print(count)
    count = count + 1

-------------------------------------------------- ------- 
the while loop of tape else, the else condition is not satisfied when performed only once.

count = 0
while count < 10:
　　print(count)
　　count = count + 1
else:
　　print("else")

-------------------------------------------------- ------- 
continue to explain: 
after encountering continue while loop will jump immediately at the beginning while the execution, that continue the current cycle times while the termination; 
COUNT usage example :( output other than 3 to 1 All figures 10)

count = 0
while count < 10:
        if count == 3:
                count =  count + 1
                continue
        print(count)
        count = count + 1

-------------------------------------------------- ------- 
break explain: 
it encounters a break immediately out of the while loop that break all the while loop terminates current; 
break, while, for example IF integrated use (user login name and password only allows users to try three times, 4th input locked account):

# -*- conding: utf-8 -*-
StrUserName = "0"
StrPassword = "0"
StrTest = "hello"
StrTest2 = "123456"
A = 0
while StrUserName != StrTest or StrPassword != StrTest2:
        A = A + 1
        if A == 4:
                print("账号锁定")
                break
        else:
                StrUserName The INPUT = ( " Please enter your user name: " ) 
                strPassword = the INPUT ( " Please enter your password: " )
                 IF strUserName == strTest and strPassword == StrTest2:
                         Print ( " Welcome " )
                 the else :
                         Print ( " account number or password is incorrect " )