php网站后台开发,一般通过什么查看天气预报,上海营销型网站制作,上海十大黑心装修公司在Python中#xff0c;可以定义包含若干参数的函数#xff0c;这里有几种可用的形式#xff0c;也可以混合使用#xff1a;1. 默认参数最常用的一种形式是为一个或多个参数指定默认值。 def ask_ok(prompt,retries4,complaintYes or no Please!):while True:ok…在Python中可以定义包含若干参数的函数这里有几种可用的形式也可以混合使用1. 默认参数最常用的一种形式是为一个或多个参数指定默认值。 def ask_ok(prompt,retries4,complaintYes or no Please!):while True:okinput(prompt)if ok in (y,ye,yes):return Trueif ok in (n,no,nop,nope):return Falseretriesretries-1if retries0:raise IOError(refusenik user)print(complaint)这个函数可以通过几种方式调用只提供强制参数 ask_ok(Do you really want to quit?)Do you really want to quit?yesTrue提供一个可选参数 ask_ok(OK to overwrite the file,2)OK to overwrite the fileNoYes or no Please!OK to overwrite the filenoFalse提供所有的参数 ask_ok(OK to overwrite the file?,2,Come on, only yes or no!)OK to overwrite the file? testCome on, only yes or no!OK to overwrite the file?yesTrue2. 关键字参数函数同样可以使用keywordvalue形式通过关键字参数调用 def parrot(voltage,statea stiff,actionvoom,typeNorwegian Blue):print(--This parrot wouldnt, action, end )print(if you put,voltage,volts through it.)print(--Lovely plumage, the,type)print(--Its,state,!) parrot(1000)--This parrot wouldnt voom if you put 1000 volts through it.--Lovely plumage, the Norwegian Blue--Its a stiff ! parrot(actionvooooom,voltage1000000)--This parrot wouldnt vooooom if you put 1000000 volts through it.--Lovely plumage, the Norwegian Blue--Its a stiff ! parrot(a thousand,statepushing up the daisies)--This parrot wouldnt voom if you put a thousand volts through it.--Lovely plumage, the Norwegian Blue--Its pushing up the daisies !但是以下的调用方式是错误的 parrot(voltage5, dead)SyntaxError: non-keyword arg after keyword arg parrot()Traceback (most recent call last):File , line 1, in parrot()TypeError: parrot() missing 1 required positional argument: voltage parrot(110, voltage220)Traceback (most recent call last):File , line 1, in parrot(110, voltage220)TypeError: parrot() got multiple values for argument voltage parrot(actorJohn)Traceback (most recent call last):File , line 1, in parrot(actorJohn)TypeError: parrot() got an unexpected keyword argument actor parrot(voltage100,actionvoom,actionvoooooom)SyntaxError: keyword argument repeatedPython的函数定义中有两种特殊的情况即出现***的形式。*用来传递任意个无名字参数这些参数会以一个元组的形式访问**用来传递任意个有名字的参数这些参数用字典来访问(*name必须出现在**name之前) def cheeseshop1(kind,*arguments,**keywords):print(--Do you have any,kind,?)print(--Im sorry, were all out of,kind)for arg in arguments:print(arg)print(-*40)keyssorted(keywords.keys())for kw in keys:print(kw,:,keywords[kw]) cheeseshop1(Limbuger,Its very runny, sir.,Its really very, very runny, sir.,shopkeeperMichael Palin,clientJohn,sketchCheese Shop Sketch)--Do you have any Limbuger ?--Im sorry, were all out of LimbugerIts very runny, sir.Its really very, very runny, sir.----------------------------------------client : Johnshopkeeper : Michael Palinsketch : Cheese Shop Sketch3. 可变参数列表最常用的选择是指明一个函数可以使用任意数目的参数调用。这些参数被包装进一个元组在可变数目的参数前可以有零个或多个普通的参数通常这些可变的参数在形参列表的最后定义因为他们会收集传递给函数的所有剩下的输入参数。任何出现在*args参数之后的形参只能是“关键字参数” def contact(*args,sep/):return sep.join(args) contact(earth,mars,venus)earth/mars/venus4. 拆分参数列表当参数是一个列表或元组但函数需要分开的位置参数时就需要拆分参数调用函数时使用*操作符将参数从列表或元组中拆分出来 list(range(3,6))[3, 4, 5] args[3,6] list(range(*args))[3, 4, 5]以此类推字典可以使用**操作符拆分成关键字参数 def parrot(voltage,statea stiff,actionvoom):print(--This parrot wouldnt, action,end )print(if you put,voltage,volts through it.,end )print(Es, state,!) d{voltage:four million,state:bleedin demised,action:VOOM} parrot(**d)--This parrot wouldnt VOOM if you put four million volts through it. Es bleedin demised !5. Lambda在Python中使用lambda来创建匿名函数而用def创建的是有名称的。python lambda会创建一个函数对象但不会把这个函数对象赋给一个标识符而def则会把函数对象赋值给一个变量python lambda它只是一个表达式而def则是一个语句 def make_incrementor(n):return lambda x:xn fmake_incrementor(42) f(0)42 f(2)44 glambda x:x*2 print(g(3))6 mlambda x,y,z:(x-y)*z print(m(3,1,2))46. 文档字符串关于文档字符串内容和格式的约定第一行应该总是关于对象用途的摘要以大写字母开头并且以句号结束如果文档字符串包含多行第二行应该是空行 def my_function():Do nothing, but document it.No, really, it doesnt do anything.pass print(my_function.__doc__)Do nothing, but document it.No, really, it doesnt do anything.
