Python 基础

变量和数据类型

Python 是动态类型语言，变量不需要声明类型。

基本数据类型

# 数字类型
age = 25          # 整数 (int)
height = 175.5    # 浮点数 (float)
complex_num = 3+4j # 复数 (complex)

# 字符串类型
name = "Alice"     # 字符串 (str)
message = 'Hello'  # 单引号也可以

# 布尔类型
is_student = True  # 布尔值 (bool)
is_working = False

# 空值
data = None        # NoneType

字符串操作

# 字符串拼接
first_name = "John"
last_name = "Doe"
full_name = first_name + " " + last_name

# 格式化字符串
age = 30
message = f"我的名字是 {full_name}，今年 {age} 岁"

# 字符串方法
text = "Hello World"
print(text.upper())    # HELLO WORLD
print(text.lower())    # hello world
print(text.split())    # ['Hello', 'World']

控制结构

条件语句

score = 85

if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"
else:
    grade = "F"

print(f"成绩等级: {grade}")

循环语句

# for 循环
fruits = ["苹果", "香蕉", "橙子"]
for fruit in fruits:
    print(f"我喜欢 {fruit}")

# range() 函数
for i in range(5):  # 0 到 4
    print(i)

# while 循环
count = 0
while count < 3:
    print(f"计数: {count}")
    count += 1