定义函数
def greet_user(name):
print("Hello, " + name.title() + '!')
greet_user('jesse')
Hello, Jesse!
关键字实参使得实参的传递不必严格按照形参的顺序
def describe_pet(animal_type, pet_name):
print("I have a " + animal_type + ".")
print("My " + animal_type + "'s name is " + pet_name.title() + ".")
describe_pet(animal_type='hamster', pet_name='harry')
I have a hamster.
My hamster's name is Harry.
带默认值的形参，显然有默认值的形参在参数列表中排在无默认值形参的后面
def describe_pet(pet_name, animal_type='dog'):
print("I have a " + animal_type + ".")
print("My " + animal_type + "'s name is " + pet_name.title() + ".")
describe_pet('harry')
I have a dog.
My dog's name is Harry.
简单返回值的函数
def get_formmatted_name(first_name, last_name):
full_name = first_name + ' ' + last_name
return full_name.title()
print(get_formmatted_name('jimi','hendrix'))
Jimi Hendrix
函数可返回任何类型的值，包括列表和字典
def build_person(first_name,last_name,age=''):
person = {'first': first_name, 'last': last_name}
if age:
person['age'] = age
return person
musician = build_person('jimi','hendrix',age=27)
print(musician)
{'first': 'jimi', 'last': 'hendrix', 'age': 27}
传递列表并修改
def greet_users(names):
for i in range(len(names)):
names[i] = names[i].title()
usernames = ['hannah', 'ty', 'margot']
greet_users(usernames)
print(usernames)
['Hannah', 'Ty', 'Margot']
当不打算改变原列表时，可传入列表的副本
def greet_users(names):
for i in range(len(names)):
names[i] = names[i].title()
usernames = ['hannah', 'ty', 'margot']
greet_users(usernames[:])
print(usernames)
['hannah', 'ty', 'margot']
传递任意数量的实参
def make_pizza(*toppings): #toppings 是一个元组
for topping in toppings:
print(topping)
make_pizza('pepperoni')
make_pizza('mushroooms','green peppers','extra cheese')
pepperoni
mushroooms
green peppers
extra cheese
结合使用位置实参和任意数量实参
def make_pizza(size, *toppings):
print("\nMaking a " + str(size) + "-inch pizza with the following toppings:")
for topping in toppings:
print("- " + topping)
make_pizza(16, 'pepperoni')
make_pizza(12, 'mushrooms', 'green peppers', 'extra cheese')
Making a 16-inch pizza with the following toppings:
- pepperoni
Making a 12-inch pizza with the following toppings:
- mushrooms
- green peppers
- extra cheese
使用任意数量的关键字实参，很多库的API都这么设计
def build_profile(first, last, **user_info):
profile = {}
profile['first_name'] = first
profile['last_name'] = last
for key, value in user_info.items():
profile[key] = value
return profile
user_profile1 = build_profile('albert','einstein',
location='princton',field='physics')
user_profile2 = build_profile('marie','curie',
user_info={'location':'paris','field':'pthsics'})
#不能这么写
#user_profile2 = build_profile('marie','curie',
# {'location':'paris','field':'pthsics'})
u3info = {'location': 'london','field': 'computer'}
user_profile3 = build_profile('turing','alen',**u3info)
print(user_profile1)
print(user_profile2)
print(user_profile3)
{'first_name': 'albert', 'last_name': 'einstein', 'location': 'princton', 'field': 'physics'}
{'first_name': 'marie', 'last_name': 'curie', 'user_info': {'location': 'paris', 'field': 'pthsics'}}
{'first_name': 'turing', 'last_name': 'alen', 'location': 'london', 'field': 'computer'}
将函数存储为单独的模块
将pizza.py与making_pizzas.py置于同一目录
pizza.py内容
def make_pizza(size, *toppings):
print("\nMaking a "+str(size) + '-inch pizza with the following toppings:')
for topping in toppings:
print('-' + topping)
making_pizzas.py 通过 import 导入 pizza 模块
import pizza
pizza.make_pizza(16, 'pepperoni')
pizza.make_pizza(12, 'mushrooms', 'green pepers', 'extra cheese')
导入特定的函数
from pizza import make_pizza
make_pizza(16, 'pepperoni')
make_pizza(12, 'mushrooms', 'green pepers', 'extra cheese')
使用as给函数指定别名
from pizza import make_pizza as mp
mp(16, 'pepperoni')
mp(12, 'mushrooms', 'green pepers', 'extra cheese')
as也可以给模块起别名
import pizza as p
p.make_pizza(16, 'pepperoni')
p.make_pizza(12, 'mushrooms', 'green pepers', 'extra cheese')