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Python语言之控制流(if...elif...else,while,for,break,continue)

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

 1 number = 23 2 guess = int(raw_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(raw_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 that12     else:13         print No, it is a little lower than that14 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 i3 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。

Python语言之控制流(if...elif...else,while,for,break,continue)