[Python知识库]Python编程从入门到实践~函数

定义函数

#定义函数
def greet_user():
	print("Hello~")

#调用函数
greet_user()


#向函数传递信息
def print_user(username):
	print(f"Hello~{username}")

print_user('Jesse')

传递实参数

#位置实参
def describe_pet(animal_type, pet_name):
	print(f"I have a {animal_type}")
	print(f"My {animal_type}'s name is {pet_name.title()}")

describe_pet('hamster', 'harry')


#关键字实参数&默认值
def describe_peet(animal_type='haster', pet_name='harry'):
	print(f"I have a {animal_type}")
	print(f"My {animal_type}'s name is {pet_name.title()}")

describe_peet()
describe_peet(pet_name='Zhangsan', animal_type='human')

返回值

#返回简单值
def get_formatted_name(first_name, last_name):
	full_name = f"{first_name} {last_name}"
	return full_name.title()

musician = get_formatted_name('jimi', 'hendrix')
print(musician)



#让实参数可选
def formatted_name(first_name, last_name, middle_name=''):
	full_name = f"{first_name} {middle_name} {last_name}"
	return full_name.title()

musician = formatted_name('jimi', 'hendrix')
print(musician)
musician = formatted_name('jimi', 'hendrix', 'lee')
print(musician)

传递列表

#在函数中修改列表
def print_models(unprinted_designs, completed_models):
	while unprinted_designs:
		current_design = unprinted_designs.pop()
		print(f"Printing model:{current_design}")
		completed_models.append(current_design)

def show_completed_models(completed_models):
	print("The following models have been printed:")
	for completed_model in completed_models:
		print(completed_model)

unprinted_designs = ['phone case', 'robot pendant', 'dodecahedron']
completed_models = []
print_models(unprinted_designs, completed_models)
show_completed_models(completed_models)



#禁止函数修改列表
print_models(unprinted_designs[:], completed_models)

传递任意数量的实参

#传递任意数量的实参数
def make_pizza(*toppings):
	print(toppings)

make_pizza('pepperoni')
make_pizza('mushrooms', 'green peppers', 'extra cheese')


#结合使用位置实参和任意数量实参
def make_pizza_size(size, *toppings):
	print(f"Making a {size} pizza with the following toppings:")
	for top in toppings:
		print(f"-{top}")

make_pizza_size(16, 'pepperoni')
make_pizza_size(12, 'mushrooms', 'green peppers', 'extra cheese')


#使用任意数量的关键字实参数
def build_profile(first, last, **user_info):
	user_info['first_name'] = first
	user_info['last_name'] = last
	return user_info

user_info = build_profile('albert', 'einstein', location='princeton', field='physics')
print(user_info)

将函数存储在模块中

1、导入整个模块

pizza.py

def make_pizza(size, *toppings):
	print(f"Making a {size} pizza with the following toppings:")
	for top in toppings:
		print(f"-{top}")

pizza_main.py

import pizza

pizza.make_pizza(16, 'pepperoni')
pizza.make_pizza(12, 'mushrooms', 'green peppers', 'extra cheese')

2、导入特定的函数

#导入单个函数
from module_name import function_name


#导入多个函数
from module_name import function_0, function_1

from pizza import make_pizza

make_pizza(16, 'pepperoni')
make_pizza(12, 'mushrooms', 'green peppers', 'extra cheese')

3、使用 as 给函数指定别名

from pizza import make_pizza as mp

mp(16, 'pepperoni')
mp(12, 'mushrooms', 'green peppers', 'extra cheese')

4、使用 as 给模块指定别名

import pizza as p

p.make_pizza(16, 'pepperoni')
p.make_pizza(12, 'mushrooms', 'green peppers', 'extra cheese')

函数编写指南

给形参指定默认值时，等号两边不要有空格：

def function_name(parameter_0, parameter_1='default value')

对于函数调用中的关键实参，也遵循整个约定

function_name(value_0, parameter_1='value')

函数参数缩进对齐

def function_name(
    parameter_0, parameter_1, parameter_2,
    parameter_3, parameter_4, parameter_5):

使用空行分隔多个函数

所有import 语句都放在文件开头