Python 进阶

函数

函数定义和调用

def greet(name, age=18):
    """问候函数，带有默认参数"""
    return f"你好，{name}！你今年 {age} 岁。"

# 函数调用
message1 = greet("Alice")
message2 = greet("Bob", 25)
print(message1)  # 你好，Alice！你今年 18 岁。
print(message2)  # 你好，Bob！你今年 25 岁。

可变参数

def sum_numbers(*args):
    """计算任意数量数字的和"""
    return sum(args)

def print_info(**kwargs):
    """打印关键字参数信息"""
    for key, value in kwargs.items():
        print(f"{key}: {value}")

# 使用示例
result = sum_numbers(1, 2, 3, 4, 5)  # 15
print_info(name="Alice", age=25, city="北京")

面向对象编程

类和对象

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age
    
    def introduce(self):
        return f"我是 {self.name}，今年 {self.age} 岁"
    
    def have_birthday(self):
        self.age += 1
        print(f"{self.name} 过生日了！现在 {self.age} 岁")

# 创建对象
person1 = Person("Alice", 25)
print(person1.introduce())
person1.have_birthday()

继承

class Student(Person):
    def __init__(self, name, age, student_id):
        super().__init__(name, age)
        self.student_id = student_id
        self.courses = []
    
    def enroll_course(self, course):
        self.courses.append(course)
        print(f"{self.name} 选修了 {course} 课程")
    
    def introduce(self):
        base_intro = super().introduce()
        return f"{base_intro}，学号是 {self.student_id}"

# 使用继承
student = Student("Bob", 20, "S001")
print(student.introduce())
student.enroll_course("Python编程")

异常处理

def divide_numbers(a, b):
    try:
        result = a / b
        return result
    except ZeroDivisionError:
        print("错误：除数不能为零")
        return None
    except TypeError:
        print("错误：参数必须是数字")
        return None
    finally:
        print("计算完成")

# 使用示例
print(divide_numbers(10, 2))   # 5.0
print(divide_numbers(10, 0))   # 错误：除数不能为零
print(divide_numbers(10, "a")) # 错误：参数必须是数字

文件操作

# 写入文件
with open("example.txt", "w", encoding="utf-8") as file:
    file.write("Hello, Python!\n")
    file.write("这是第二行\n")

# 读取文件
with open("example.txt", "r", encoding="utf-8") as file:
    content = file.read()
    print(content)

# 逐行读取
with open("example.txt", "r", encoding="utf-8") as file:
    for line in file:
        print(line.strip())

列表推导式

# 基本列表推导式
numbers = [1, 2, 3, 4, 5]
squares = [x**2 for x in numbers]
print(squares)  # [1, 4, 9, 16, 25]

# 带条件的列表推导式
even_squares = [x**2 for x in numbers if x % 2 == 0]
print(even_squares)  # [4, 16]

# 字典推导式
word_lengths = {word: len(word) for word in ["apple", "banana", "cherry"]}
print(word_lengths)  # {'apple': 5, 'banana': 6, 'cherry': 6}