类中不同方法能否有不同参数？如何为用户类可选添加年龄属性？

1. Technical Question: Can different methods in a class have different parameters? #

Absolutely yes! There’s no rule that forces all methods in a class to share the same parameter list. Each method exists to serve a specific purpose, so their parameters should be tailored to what that method needs to do.

For example, a User class might have a login method that requires username and password, and a send_message method that takes recipient and content—these two methods clearly have different parameters, and that’s totally normal and encouraged for clean, functional code.

2. Implementation Suggestions for Your User Class & Age Requirement #

First, let’s fix the obvious bugs in your existing code:

• In the __init__ method, you tried to assign name to self.name, but the parameter you received is user_name—so it should be self.name = user_name.
• There’s a typo: self.mun_id should be self.num_id to match the parameter num_id.

Now, for your requirement (adding an age attribute in a separate method, with some users not having an age), here’s a clean, Pythonic implementation:

class User:
    """A class to save info about every user"""
    def __init__(self, user_name, num_id):
        self.name = user_name
        self.num_id = num_id
        self.age = None  # Initialize age as None for users without age data

    def set_age(self, age):
        """Independent method to set the user's age"""
        self.age = age

# Usage examples
user1 = User("martin", "1")
print(user1.name)  # Output: martin
print(user1.age)   # Output: None (no age set yet)

# Set age later using the dedicated method
user1.set_age(28)
print(user1.age)   # Output: 28

# Another user who might never have an age set
user2 = User("lisa", "3")
print(user2.age)   # Output: None

Why this works: #

• Initializing self.age = None makes it clear that the user doesn’t have an age value yet, instead of leaving the attribute undefined (which could cause errors later).
• Renaming the method to set_age follows Python’s naming conventions (verbs for methods that modify state), making your code more readable for other developers.

If you also want the option to set age when creating a user, you can modify the __init__ method to accept an optional age parameter while keeping the set_age method:

class User:
    """A class to save info about every user"""
    def __init__(self, user_name, num_id, age=None):
        self.name = user_name
        self.num_id = num_id
        self.age = age

    def set_age(self, age):
        """Independent method to set or update the user's age"""
        self.age = age

# Usage example with age provided upfront
user3 = User("bob", "4", 35)
print(user3.age)   # Output: 35

内容的提问来源于stack exchange，提问作者Weed Cookie