python-函数

定义：

def 函数名（参数列表）:

      函数体

eg:
   def fibonacci (n):

        result = []

        a,b=0,1

        while b<n:

             result.append(b)

             a,b=b,a+b

         return result;

    print fabonacci(1000)

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函数参数问题
def ask_ok(prompt, retries=4, complaint='Yes or no, please!'):

    while True:

       ok = raw_input(prompt)

       if ok in ('y', 'ye', 'yes'):

          return 1

       if ok in ('n', 'no', 'nop', 'nope'): return 0

       retries = retries - 1

       if retries < 0:

       raise IOError, 'refusenik user'

       print complaint

第一个参数是必选参数，所以函数调用时候必须要传递，第二第三个属于可选参数，可通过关键字指定
eg：
    ask_ok("Do you really want to quit") or

    ask_ok("Do you really want to quit",2) or

    ask_ok("Do you really want to quit",2,"It is so boring") or

    ask_ok("Do you really want to quit",complaint="It is so hurt") 

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利用lambda关键字构造匿名函数：

def  test(n):

     return lambda x: x * n

f = test(23)

print f(1)

print f(2)