6.返回字典
函数可一返回任何类型的值，包括列表和字典等较复杂的数据结构。
def build_guest_dict(last_name,first_name,age):
guset = {'last_name':last_name,'first_name':first_name,'age':age}
return guset
poet = build_guest_dict('bai','li',33)
print(poet)
{'last_name': 'bai', 'first_name': 'li', 'age': 33}
对以上函数进行扩展，加入更多形参
def build_guest_dict2(last_name,first_name,age=None,job=None):
guest = {'last_name':last_name.title(),'first_name':first_name.title()}
if age:
guest['age'] = age
if job:
guest['job'] = job.title()
return guest
poet = build_guest_dict2('du','fu',39)
print(poet)
{'last_name': 'Du', 'first_name': 'Fu', 'age': 39}
{'last_name': 'Wang', 'first_name': 'Wei', 'job': 'Singer'}
7.结合使用函数和while循环
def get_formatted_name3(last_name,first_name):
full_name = f"{last_name} {first_name}"
return full_name.title()
while True:
print('Tell me your last_name')
print("(Enter 'q' at any time to quit.)")
l_name = input('last_name')
if l_name == 'q':
break
f_name = input('first_name')
if f_name == 'q':
break
full_names = get_formatted_name3(l_name,f_name)
print(f"Hellow {full_names}")
Tell me your last_name
(Enter 'q' at any time to quit.)
last_name>? wang
first_name>? zejing
Hellow Wang ZejingTell me your last_name
(Enter 'q' at any time to quit.)
last_name>? wang
first_name>? wei
Hellow Wang WeiTell me your last_name
(Enter 'q' at any time to quit.)
last_name>? su
first_name>? shi
Hellow Su ShiTell me your last_name
(Enter 'q' at any time to quit.)
last_name>? q
8.传递列表
向函数传递列表很有用。将列表传递给函数后，函数就能直接访问其内容。
def greet_user(names):
for name in names:
message = f"hello,{name.title()}"
print(message)
usernames = ['li bai','zhang jiu ling','su dong po']
greet_user(usernames)
hello,Li Bai
hello,Zhang Jiu Ling
hello,Su Dong Po
9.在函数中修改列表
将列表传递给函数后，函数就可以对其进行修改，从而实现大批量处理数据。
unverified_users = ['Jack','Lance','Jhon','Sarapy']
verified_users = []
while unverified_users: #该循环持续弹出unverified_users列表中的元素，并追加至verified_users列表中。前列表为空时终止循环。
verifying_user = unverified_users.pop()
print(f"Now check the user: {verifying_user}")
verified_users.append(verifying_user)
print(f"The following users have verified:")
for verified_user in verified_users: #该循环遍历verified_users并打印
print(verified_user)
Now check the user: Sarapy
Now check the user: Jhon
Now check the user: Lance
Now check the user: Jack
The following users have verified:
Sarapy
Jhon
Lance
Jack
以下通过定义两个函数，完成相同的工作。
def verify_users(unverified_users,verified_users):
while unverified_users:
verifying_user = unverified_users.pop()
print(f"Now check the user: {verifying_user}")
verified_users.append(verifying_user)
def show_verified_user(verified_users):
print(f"THe follow users have verified:")
for verified_user in verified_users:
print(verified_user)
unverified_users2 = ['zhang heng','zu chong zhi','yang hui ','si ma guang']
verified_users2 = []
verify_users(unverified_users2,verified_users2)
show_verified_user(verified_users2)
Now check the user: si ma guang
Now check the user: yang hui
Now check the user: zu chong zhi
Now check the user: zhang heng
THe follow users have verified:
si ma guang
yang hui
zu chong zhi
zhang heng
每个函数都应该只负责一项具体的工作，同使函数中也可以调用函数。
10.禁止函数修改列表
有时候，需要函数调用列表元素，但又不能改变原列表，这就需要保留原列表。
这时候需要将列表的副本传递给函数，见如下代码：
def verify_users(unverified_users,verified_users):
while unverified_users:
verifying_user = unverified_users.pop()
print(f"Now check the user: {verifying_user}")
verified_users.append(verifying_user)
def show_verified_user(verified_users):
print(f"THe follow users have verified:")
for verified_user in verified_users:
print(verified_user)
unverified_users2 = ['zhang heng','zu chong zhi','yang hui ','si ma guang']
verified_users2 = []
verify_users(unverified_users2[:],verified_users2) #unverified_users2[:] 表示将该列表的副本传递给函数
show_verified_user(verified_users2)
print(unverified_users2) #打印原列表，发现列表并未变化
Now check the user: si ma guang
Now check the user: yang hui
Now check the user: zu chong zhi
Now check the user: zhang heng
THe follow users have verified:
si ma guang
yang hui
zu chong zhi
zhang heng
['zhang heng', 'zu chong zhi', 'yang hui ', 'si ma guang']
11.传递任意数量的参数
python允许函数从调用语句中收集任意数量的实参
def make_noodles(*toppings):
print(toppings)
make_noodles('pepppers','beef','eggs','beans')
make_noodles('flour')
('pepppers', 'beef', 'eggs', 'beans')
('flour',)
12.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。
def make_noodles1(size,*toppings):
print(f"Make {size}-noodles with the following toppings:")
for topping in toppings:
print(f"-{topping}")
make_noodles1('thin','pappers','eggs','tomatos')
Make thin-noodles with the following toppings:
-pappers
-eggs
-tomatos
13.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，但提前不知道传递给函数的具体信息。这种情况下可以将函数编写成能接受任意数量的键值对。
以下示例中，函数接受姓和名，还接受任意数量的关键字实参。
def build_profile(last,first,**user_info):
user_info['last_name'] = last
user_info['first_name'] = first #创建了user_info字典，用于存放字典。
return user_info
user_porfile = build_profile('xiao','hu',
age = 14,
weight = '135kg',
height = '177cm')
print(user_porfile)
{'age': 14, 'weight': '135kg', 'height': '177cm', 'last_name': 'xiao', 'first_name': 'hu'}
14.前面知识的巩固与练习
(1))三明治菜单.注意形参为单星号，如函数又返回值，其返回值为元组。
*args格式的形参，用于收集任意数量的位置实参。
def make_sandwich(*toppings):
print(f"The customer need the sandwich with the following toppings:")
for topping in toppings:
print(f"\t-{topping}")
return toppings
make_sandwich('cheese','vegetables')
result = make_sandwich('pepper','romaine','cheese','chicken')
print(type(result))
The customer need the sandwich with the following toppings:
-cheese
The customer need the sandwich with the following toppings:
-pepper
(2)个人信息函数。注意最后一个形参为双星号 **user_info,如果函数有返回值，其返回值为字典。
**kwargs格式的形参，用于收集任意数量的关键字实参。
def build_profile1(last,first,**user_info):
user_info['last_name'] = last
user_info['first_name'] = first #创建了user_info字典，用于存放字典。
return user_info
user_porfile = build_profile1('wang','zejing',
age = 37,
weight = '160kg',
height = '175cm')
print(user_porfile)
print(type(user_porfile))
{'age': 37, 'weight': '160kg', 'height': '175cm', 'last_name': 'wang', 'first_name': 'zejing'}
def car_profile(brand,model,**car_info):
car_info['brand'] = brand
car_info['model'] = model
return car_info
car_profile = build_profile1('Honda','civic',color = 'blue',size = 'B')
print(car_profile)
{'color': 'blue', 'size': 'B', 'last_name': 'Honda', 'first_name': 'civic'}