（7）函数

生成指定边界的斐波那契数列的函数：

def fib(n):    a,b=0,1    while a < n:        print(a,end=',')        a,b=b,a+bfib(1000)

运行结果：

>>> ================================ RESTART ================================>>> 0,1,1,2,3,5,8,13,21,34,55,89,144,233,377,610,987,

1.带有默认值的参数：

def ask_ok(prompt, retries=4, complaint='Yes or no, please!'):    while True:        ok = input(prompt)        if ok in ('y', 'ye', 'yes'):            return True        if ok in ('n', 'no', 'nop', 'nope'):            return False        retries = retries - 1        if retries < 0:            raise IOError('refusenik user')        print(complaint)

调用方法：

只给出必要的参数: ask_ok('Do you really want to quit?')给出一个可选的参数: ask_ok('OK to overwrite the file?', 2)或者给出所有的参数: ask_ok('OK to overwrite the file?', 2, 'Come on, only yes or no!')

2.关键字参数：key=value的形式调用：

示例1.

def parrot(voltage, state='a stiff', action='voom', type='Norwegian Blue'):    print("-- This parrot wouldn't", action, end=' ')    print("if you put", voltage, "volts through it.")    print("-- Lovely plumage, the", type)    print("-- It's", state, "!")

调用方法：

parrot(1000)                                          # 1 positional argumentparrot(voltage=1000)                                  # 1 keyword argumentparrot(voltage=1000000, action='VOOOOOM')             # 2 keyword argumentsparrot(action='VOOOOOM', voltage=1000000)             # 2 keyword argumentsparrot('a million', 'bereft of life', 'jump')         # 3 positional argumentsparrot('a thousand', state='pushing up the daisies')  # 1 positional, 1 keyword

示例2：引入一个形如 **name 的参数时，它接收一个字典，使用一个形如 *name 的形式参数，它接收一个元组。*name 必须在 **name 之前出现。

def cheeseshop(kind, *arguments, **keywords):    print("-- Do you have any", kind, "?")    print("-- I'm sorry, we're all out of", kind)    for arg in arguments:        print(arg)    print("-" * 40)    keys = sorted(keywords.keys())    for kw in keys:        print(kw, ":", keywords[kw])

调用：

>>> ================================ RESTART ================================>>> >>> cheeseshop("Limburger", "It's very runny, sir.",           "It's really very, VERY runny, sir.",           shopkeeper="Michael Palin",           client="John Cleese",           sketch="Cheese Shop Sketch")-- Do you have any Limburger ?-- I'm sorry, we're all out of LimburgerIt's very runny, sir.It's really very, VERY runny, sir.----------------------------------------client : John Cleeseshopkeeper : Michael Palinsketch : Cheese Shop Sketch>>>

3.可变参数列表：

def write_multiple_items(file, separator, *args):    file.write(separator.join(args))

调用：

>>> ================================ RESTART ================================>>> >>> def concat(*args, sep="/"):    return sep.join(args)>>> concat("earth", "mars", "venus")'earth/mars/venus'>>> concat("earth", "mars", "venus", sep=".")'earth.mars.venus'>>> 

lambda形式：

def make_incrementor(n):    return lambda x: x + n

运行：

>>> ================================ RESTART ================================>>> >>> f=make_incrementor(42)>>> f(0)42>>> f(1)43>>>