1.if...elif...else...

1 number = 23 2 guess = int(input('Enter an integer : ')) 3  4 if guess == number: 5     print( 'Congratulations, you guessed it.' ) # New block starts here 6     print( "(but you do not win any prizes!)" ) # New block ends here 7 elif guess < number: 8     print( 'No, it is a little higher than that' )# Another block 9 else:10     print( 'No, it is a little lower than that' )11 12 print( 'Done' )13 # This last statement is always executed, after the if statement is executed

 

 

2.while

1 number = 23 2 running = True 3  4 while running: 5     guess = int(input('Enter an integer : ')) 6  7     if guess == number: 8         print( 'Congratulations, you guessed it.' ) 9         running = False # this causes the while loop to stop10     elif guess < number:11         print( 'No, it is a little higher than that' )12     else:13         print( 'No, it is a little lower than that' )14 else:15     print( 'The while loop is over.' )16     # Do anything else you want to do here17 18 print( 'Done' )

while循环条件变为False时，else块被执行。

你可能想问，这样的else块始终会被执行到，还要else干嘛。别着急，在4.break中有解答。

3.for

1 for i in range(1, 5):2     print( i )3 else:4     print ( 'The for loop is over' )

range(n, m [,stepLen]) = [n,n+stepLen,n+stepLen*2,...,n+(ceil((m-n)/stepLen)-1)*stepLen]

即从n开始，以stepLen为步长，一直到小于m的序列（不包括m）。默认情况下stepLen=1。

4.break

终止当前循环语句。

注意如果从for或while循环终止，任何对应的else将不会被执行。

5.continue

跳过当前循环块中的剩余语句，然后继续进行下一轮的循环。