python的循环，pass和DocString

python的循环，pass和DocString

先来说说最简单的while循环和for循环：

while循环和C的相似性更高：

while 1>0: guess=int(input('enter a number: ')) if guess==23: print 'guess right!' break elif guess>23: print 'higher' else : print 'lower'print 'the loop1 is over'

注意for的写法:

for i in range(1,10,3): # equal to C: for(int i=1;i<10;i+=2) print ielse: # else statement can follow loop print 'the loop2 is over'

它们的输出：

>>> enter a number: 2lowerenter a number: 44higherenter a number: 23guess right!the loop1 is over147the loop2 is over>>>

pass在python函数中代表不返回值，或者说是返回None，类似于C的return ;

def maxnum(a,b): if a>b: return a else : pass #return none statement print maxnum(23,45)print maxnum(45,23)>>> None45>>>

接下来聊聊DocString：

其全称是documentation strings。它放在函数的第一行，能输出提示信息，帮助函数更容易理解，使用函数的__doc__（双下划线）来输出信息。

def midfind(a,lx,rx,goal): ''' this is a half find for ourneed number, the return is goal number's place.''' low=lx high=rx while low<=high: mid=(low+high)>>1 if a[mid]>goal: high=mid-1 elif a[mid]>> 2 this is a half find for ourneed number, the return is goal number's place.>>>

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