python(16)函数(3)
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==================================1.传递列表
将列表传递给函数后,函数就能直接访问其内容
假设有一个用户列表,要问候其中的每位用户 def greet_users(names): """向列表中的每位用户都发出简单的问候""" for name in names: msg = "hello, " + name +"!" print(msg) usernames = ["da ming", "ling ling", "ni ni"]#定义一个用户列表 greet_users(usernames)#调用greet_users,并将这个列表传递给他 hello, da ming! hello, ling ling! hello, ni ni! 2.在函数中修改列表
将列表传递给函数后,函数就可对其进行修改,在函数中对这个列表所做的任何修改都是永久性的
一家为用户提交的设计制作3D打印模型的公司,需要打印的设计存储在一个列表中,打印后转移到另一个列表中。 #创建一个列表,其中包含一些要打印的设计 unprinted_designs = ["apple", "banana", "pear"] completed_models = [] #模拟打印每个设计,直到没有未打印的设计为止 #打印每个设计后,都将其转移到列表completed_models中 while unprinted_designs: current_design = unprinted_designs.pop() #模拟根据设计制作3D打印模型的过程 print("printing model : " + current_design) completed_models.append(current_design) #显示打印好的所有模型 print(" the following models have been printed: ") for completed_model in completed_models: print(completed_model) printing model : pear printing model : banana printing model : apple the following models have been printed: pear banana apple ============================================ #改为函数模式,编写两个函数 def print_models(unprinted_models, completed_models):#第一个函数,负责处理打印设计的工作 #模拟打印每个设计,直到没有未打印的设计为止 #打印每个设计后,都将其转移到列表completed_models中 while unprinted_designs: current_design = unprinted_designs.pop() #模拟根据设计制作3D打印模型的过程 print("printing model : " + current_design) completed_models.append(current_design) def show_completed_models(completed_models):#概述打印了哪些设计 #显示打印好的所有模型 print(" the following models have been printed: ") for completed_model in completed_models: print(completed_model) unprinted_designs = ["apple", "banana", "pear"] completed_models = [] print_models(unprinted_designs, completed_models) show_completed_models(completed_models) printing model : pear printing model : banana printing model : apple the following models have been printed: pear banana apple 3.禁止函数修改列表
有时候需要禁止函数修改列表,为解决这个问题,可想向函数传递列表的副本而不是元件;这样函数所做的任何修改都只影响副本,不影响元件 #切片法[:]代表创建列表的副本 print_models(unprinted_designs[:], completed_models) 4.传递任何数量是实参
有时候,预先布置的函数需要接受多少个实参,python允许函数从调用语句中手机任意数量的实参
一个制作披萨的寒素,它需要接受很多配料,但无法确定顾客要多少种配料,下面函数只有一个形参*toppings,不管调用语句提供了多少实参,这个形参都将他们统统收入囊中 def make_pizza(*toppings): #打印顾客点的所有配料 print(toppings) make_pizza("mo gu") make_pizza("cao mei", "xi hong shi","jiang liao") ("mo gu",) ("cao mei", "xi hong shi", "jiang liao") ======================================= #将print语句替换为一个循环 def make_pizza(*toppings): #打印顾客点的所有配料 print(" making a pizza with the following toppings :") for topping in toppings: print("- " + topping) make_pizza("mo gu") make_pizza("cao mei", "xi hong shi","jiang liao") making a pizza with the following toppings : - mo gu making a pizza with the following toppings : - cao mei - xi hong shi - jiang liao 5.结合使用位置实参和任意数量实参
如果要让函数接受不同类型的实参,必须在函数定义中将接纳任意数量实参的形参放在最后
python先匹配位置实参和关键字实参,再将余下的实参收集到最后一个形参中
如果前边的函数还需要一个表示披萨尺寸的实参,必须将该形参放在*toppings的前面 def make_pizza(size, *toppings): #打印顾客点的所有配料 print(" making a" + str(size) + "-inch pizza with the following toppings :") for topping in toppings: print("- " + topping) make_pizza(16, "mo gu") make_pizza(12, "cao mei", "xi hong shi","jiang liao") making a16-inch pizza with the following toppings : - mo gu making a12-inch pizza with the following toppings : - cao mei - xi hong shi - jiang liao 6.使用任意数量的关键字实参
有时候,需要接受任意数量的实参,但预先不知道传递给函数的会是射门杨的信息,再这种情况下,可将函数编写成能够接受任意数量的键-值对,调用语句提供了多少就接受多少
创建用户简介:你知道你将收到有关用户的信息,但不确定会是什么样的信息,在下面示例中,build_profile()接受名和姓,同时还接受任意数量的关键字实参 def build_profile(first, last, **user_info): #创建一个字典,其中包含我们知道的有关用户的一切 profile = {} profile["first_name"] = first profile["last_name"] = last for key, value in user_info.items(): profile[key] = value return profile user_profile = build_profile("da ming", "zhang",location="bei jing", field="bai ling") print(user_profile) {"first_name": "da ming", "last_name": "zhang", "location": "bei jing", "field": "bai ling"} 7.将函数存储在模块中###1.导入整个模块 #要让函数是可导入的,得先创建模块,模块是拓展名为.py的文件 #创建一个包含函数make_pizza的模块 def make_pizza(size, *toppings): #打印顾客点的所有配料 print(" making a" + str(size) + "-inch pizza with the following toppings :") for topping in toppings: print("- " + topping) #在pizza.py所在的目录中创建另一个名为making_pizza.py的文件,这个文件导入刚创建的模块,使用import语句 import pizza pizza.make_pizza(16, "mo gu") pizza.make_pizza(12, "cao mei", "xi hong shi","jiang liao") making a16-inch pizza with the following toppings : - mo gu making a12-inch pizza with the following toppings : - cao mei - xi hong shi - jiang liao =========================================== #导入特定的函数 #还可以导入模块中特定的函数,语法如下: from module_name import function_name #通过用逗号分隔函数名,可根据需要从模块中导入任意数量的函数 from module_name import function_0, function_1, function_2 #对于前面的making_pizza.py示例,如果只想导入使用的函数 from pizza import make_pizza pizza.make_pizza(16, "mo gu") pizza.make_pizza(12, "cao mei", "xi hong shi","jiang liao") making a16-inch pizza with the following toppings : - mo gu making a12-inch pizza with the following toppings : - cao mei - xi hong shi - jiang liao ================================================= #使用as函数指定别名 #可以将导入的函数名称改为自己喜欢的名字 from pizza import make_pizza as mp mp(16, "mo gu") mp(12, "cao mei", "xi hong shi","jiang liao") #通用语法 from module_name import function_name as fn ================================================ #使用as给模块指定别名 import pizza as p p.make_pizza(16, "mo gu") p.make_pizza(12, "cao mei", "xi hong shi","jiang liao") #通用语法 import module_name as mn ============================================== #导入模块中的所有函数:使用星号* from pizza import * make_pizza(16, "mo gu") make_pizza(12, "cao mei", "xi hong shi","jiang liao") #通用语法 from module_name import *