Python初学者入门指南八大要点

# 第一个Python程序
print("Hello, World!")
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Hello, World!
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# 定义变量
a = 10        # 整数
b = 3.14      # 浮点数
c = "Hello"    # 字符串
d = [1, 2, 3]  # 列表
e = (1, 2, 3)  # 元组
f = {"name": "Alice", "age": 25}  # 字典
g = {1, 2, 3}  # 集合

# 输出变量
print(a, b, c, d, e, f, g)
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10 3.14 Hello [1, 2, 3] (1, 2, 3) {'name': 'Alice', 'age': 25} {1, 2, 3}
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# 条件语句
x = 10
if x > 5:
    print("x 大于 5")
elif x == 5:
    print("x 等于 5")
else:
    print("x 小于 5")

# 循环
for i in range(5):
    print(i)

# while 循环
count = 0
while count < 5:
    print(count)
    count += 1
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x 大于 5
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# 定义函数
def greet(name):
    print(f"Hello, {name}!")

# 调用函数
greet("Alice")

# 导入模块
import math
print(math.sqrt(16))
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Hello, Alice!
**4.**0
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# 写入文件
with open("example.txt", "w") as file:
    file.write("Hello, Python!\n")

# 读取文件
with open("example.txt", "r") as file:
    content = file.read()
    print(content)
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Hello, Python!
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try:
    # 尝试执行的代码
    result = 10 / 0
except ZeroDivisionError:
    # 处理除以零的异常
    print("不能除以零")
else:
    # 如果没有异常发生
    print(f"结果是: {result}")
finally:
    # 无论是否发生异常都会执行
    print("执行完毕")
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不能除以零
执行完毕
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# 定义类
class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def greet(self):
        print(f"Hello, my name is {self.name} and I am {self.age} years old.")

# 创建对象
alice = Person("Alice", 30)
alice.greet()
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Hello, my name is Alice and I am 30 years old.
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class Student:
    def __init__(self, name, score):
        self.name = name
        self.score = score

    def display_info(self):
        print(f"{self.name} 的成绩是 {self.score}")

def add_student(students, name, score):
    if 0 <= score <= 100:
        students.append(Student(name, score))
    else:
        print("成绩必须在0到100之间")

def calculate_average(students):
    if not students:
        return 0
    total_score = sum(student.score for student in students)
    return total_score / len(students)

def main():
    students = []
    while True:
        print("\n1. 添加学生")
        print("2. 显示所有学生信息")
        print("3. 计算平均分")
        print("4. 退出")
        
        choice = input("请选择操作: ")
        
        if choice == '1':
            name = input("输入学生姓名: ")
            score = int(input("输入学生成绩: "))
            add_student(students, name, score)
        elif choice == '2':
            for student in students:
                student.display_info()
        elif choice == '3':
            avg_score = calculate_average(students)
            print(f"平均成绩是: {avg_score:.2f}")
        elif choice == '4':
            break
        else:
            print("无效选择，请重新输入")

if __name__ == "__main__":
    main()
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