Python基础教程

1. 变量 (Variables)

变量是用来存储数据的容器。在Python中，你可以直接给变量赋值，无需声明类型。

# Variable assignment examples
name = "John"
age = 25
height = 1.75

Python会自动识别数据类型：字符串、整数、浮点数等。

2. 数据类型 (Data Types)

Python有以下基本数据类型：

# Data type examples
text = "Hello World"      # String
number = 42               # Integer
decimal = 3.14            # Float
is_true = True            # Boolean
items = [1, 2, 3]         # List

3. 基本运算 (Basic Operations)

Python支持各种数学和逻辑运算：

# Arithmetic operations
a = 10 + 5    # Addition
b = 10 - 3    # Subtraction
c = 10 * 2    # Multiplication
d = 10 / 3    # Division

# Comparison operations
x = 5 > 3     # True
y = 5 < 3     # False
z = 5 == 5    # True

4. 条件语句 (Conditional Statements)

使用if、elif、else来根据条件执行不同的代码块：

age = 18

if age < 18:
    print("Underage")
elif age == 18:
    print("Just turned adult")
else:
    print("Adult")

5. 列表 (Lists)

列表是存储多个项目的有序集合：

# Create a list
fruits = ["Apple", "Banana", "Orange"]

# Access element
first_fruit = fruits[0]    # "Apple"

# Add element
fruits.append("Grape")

# Iterate over list
for fruit in fruits:
    print(fruit)

6. For循环 (For Loops)

For循环用于遍历序列中的每个元素：

# Iterate over list
animals = ["Dog", "Cat", "Bird"]
for animal in animals:
    print("I like", animal)

# Numeric loop
for i in range(5):
    print("Number:", i)

7. While循环 (While Loops)

While循环在条件为真时重复执行代码块。这是《The Farmer Was Replaced》中最重要的循环结构：

# Basic while loop
count = 0
while count < 5:
    print("Count:", count)
    count = count + 1

# Infinite loop (common in games)
while True:
    # Get the next action
    action = get_next_action()
    if action == "Stop":
        break
    execute_action(action)

8. 函数 (Functions)

函数是可重用的代码块，用于执行特定任务：

# Define function
def greet(name):
    return "Hello, " + name + "!"

# Call function
message = greet("Xiao Ming")
print(message)

# Function with multiple parameters
def calculate_area(length, width):
    return length * width

area = calculate_area(5, 3)
print("Area:", area)