python函数-易错知识点

定义函数：

def greet_users(names): #names是形参
    """Print a simple greeting to each user in the list."""
    for name in names:
        msg = "Hello, " + name.title() + "!"
        print(msg)

usernames = ['hannah', 'ty', 'margot']
greet_users(usernames)#usernames是实参

关键字def来定义一个函数。实参是调用函数时传递给函数的的信息。

调用函数时，把实参传递给函数，这个值被存储在形参中。PS:大脑中有这个概念，至于如何使用，按实际情况来考虑。

传递实参：

def describe_pet(pet_name, animal_type='dog'):
#关联方式：位置实参；animal_type指定了默认名。若调用函数未给形参提供实参，则使用默认名。
    """Display information about a pet."""
    print("
I have a " + animal_type + ".")
    print("My " + animal_type + "'s name is " + pet_name.title() + ".")
    
# A dog named Willie.
describe_pet('willie')
describe_pet(pet_name='willie')

# A hamster named Harry.
describe_pet('harry', 'hamster')
describe_pet(pet_name='harry', animal_type='hamster')
#使用关键词实参，务必准确地指定函数定义的形参名
describe_pet(animal_type='hamster', pet_name='harry')

• 1.调用函数多次
• 2.位置实参的顺序很重要

 返回值：

def get_formatted_name(first_name, last_name, middle_name=''):、
#让实参变成可选的，形参=‘空字符串’。
    """Return a full name, neatly formatted."""
    if middle_name:
        full_name = first_name + ' ' +  middle_name + ' ' + last_name
    else:
        full_name = first_name + ' ' + last_name
    return full_name.title()  #返回
    
musician = get_formatted_name('jimi', 'hendrix')
print(musician)

musician = get_formatted_name('john', 'hooker', 'lee')
print(musician)

 返回字典：

def build_person(first_name, last_name, age=''):
    """Return a dictionary of information about a person."""
    person = {'first': first_name, 'last': last_name}
    if age:
        person['age'] = age
    return person
#返回字典，将值封装到字典中
musician = build_person('jimi', 'hendrix', age=27)
print(musician)

传递列表：

将列表传递给函数后，函数能直接访问其内容。

def greet_users(names):
    """Print a simple greeting to each user in the list."""
    for name in names:
        msg = "Hello, " + name.title() + "!"
        print(msg)

usernames = ['hannah', 'ty', 'margot'] #列表调用定义的函数，将列表传递给形参。
greet_users(usernames)

在函数中修改列表：

def print_models(unprinted_designs, completed_models):                 #定义函数1
    """
    Simulate printing each design, until there are none left.
    Move each design to completed_models after printing.
    """
    while unprinted_designs:
        current_design = unprinted_designs.pop()
    
        # Simulate creating a 3d print from the design.
        print("Printing model: " + current_design)
        completed_models.append(current_design)      #在函数中修改列表
        
def show_completed_models(completed_models):                       #定义函数2
    """Show all the models that were printed."""
    print("
The following models have been printed:")
    for completed_model in completed_models:
        print(completed_model)
        
        
unprinted_designs = ['iphone case', 'robot pendant', 'dodecahedron']
completed_models = []

print_models(unprinted_designs, completed_models)
show_completed_models(completed_models)

 导入函数：

from 模块 import 函数 as 简标记

*代表所有函数