Day - Types of arguments in Python

Python function parameter type Detailed explanation

This article will explain the different types of functional parameters in Python, including position parameters, variable length parameters, keyword parameters, default parameters, keywords variable parameters, and keywords for only parameters. In addition, we will also explore related concepts such as global variables, local variables, nested functions, and variable default parameters.

<.> 1. Position parameter (Positive Arguments)

The value of the position parameters is assigned to the parameter in order in order.

<.> 2. variable long parameter (variable-specific arguments)

def greet(first_name, last_name):
    print("欢迎,", first_name, last_name)

greet("张三", "李四")  # 输出：欢迎, 张三 李四

def calculate_sum(numbers):
    total = 0
    for number in numbers:
        total += number
    print(total)

scores = [80, 90, 75]
calculate_sum(scores)  # 输出：245

Also known as any parameter, allowing the function to accept the number of variable parameters. Use <表示> prefix representation.

<.> 3. Keyword arguments

* The parameter assignment can be passed without passing the parameters when calling the function.

def calculate_sum(*numbers):
    total = 0
    for number in numbers:
        total += number
    print(total)

calculate_sum(10, 20, 30)  # 输出：60
calculate_sum(5, 15, 25, 35)  # 输出：80
calculate_sum()  # 输出：0

<.> 4. default parameter (default arguments)

The parameter has the default value, and the parameter can be omitted when calling the function.

def greet(name, greeting="你好"):
    print(greeting, name)

greet(name="王五", greeting="早上好")  # 输出：早上好 王五
greet(name="赵六")  # 输出：你好 赵六

<.> 5. Keyword variable-level-specific arguments)

Allows to pass any number of keyword parameters, use

prefix indicates, and the parameters are stored in the form of dictionary.

def login(username, password="password123"):
    print(username, password)

login("admin")  # 输出：admin password123
login("user", "mypassword")  # 输出：user mypassword

<.> 6. Keyword-only arguments)

When calling the function, the parameter name must be specified, and the location parameters and keywords are used in the

in the function signature.

**

<.> 7. Function RETURNING DICTIONARY

def user_info(**kwargs):
    print(kwargs)

user_info(name="孙七", age=30, city="北京")  # 输出：{'name': '孙七', 'age': 30, 'city': '北京'}

Function can create and return the dictionary object. The function combines multiple list elements into a meta group, and the

function converts the tuples into a dictionary.

*

<.> 8. Mutable default arguments

def add(*, num1, num2):
    return num1 + num2

print(add(num1=100, num2=200))  # 输出：300
# print(add(100, 200))  # 报错：TypeError

When using a list or dictionary as the default parameter, it should be noted that it only initializes it once. If the default parameter is modified in the function call, the modified value will be retained in subsequent calls. It is recommended to use as the default value and create a new variable object within the function.

zip() <.> 9. Global variables dict()

def create_player_stats(names, scores):
    return dict(zip(names, scores))

names = ["A", "B", "C"]
scores = [10, 20, 30]
stats = create_player_stats(names, scores)
print(stats)  # 输出：{'A': 10, 'B': 20, 'C': 30}

Variables defined outside all functions.

<.> 10. Local variables

None Variables defined in the function or code block.

def add_to_list(number, my_list=None):
    if my_list is None:
        my_list = []
    my_list.append(number)
    return my_list

print(add_to_list(10))  # 输出：[10]
print(add_to_list(20))  # 输出：[20]

<.> 11. The nested function (inner function)

Functions defined in other functions. Internal functions can access variables of external functions. Using <字> Keywords can modify variables of external functions.

global_var = 100

def access_global():
    print(global_var)

access_global()  # 输出：100

Through the above examples, you can more clearly understand the usage and characteristics of various function parameters in Python, and avoid common errors during use. Remember, understand the trap of variable default parameters and take appropriate measures.

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