def example_function():
    for i in range(10):
        print(i)

max_count = 100  # 变量
def get_user_info():  # 函数
    pass

class StudentInfo:  # 类名
    pass

PI = 3.14159  # 常量

class MyClass:

    def method_one(self):
        pass

    def method_two(self):
        pass


def my_function():
    print("Hello, World!")

x = 10 + 5  # 正确
y = x * 2   # 正确

def func(arg1=10, arg2=20):  # 正确
    pass

# 计算圆的面积
def calculate_area(radius):
    """计算并返回圆的面积"""
    return 3.14 * radius ** 2  # 使用 π 计算面积

import os
import sys

import numpy as np
import pandas as pd

from my_project import my_module

data = (
    "This is a very long string that "
    "needs to be wrapped properly."
)

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    @classmethod
    def from_birth_year(cls, name, year):
        return cls(name, 2025 - year)

# 这是一个单行注释

'''
单引号注释
单引号注释
'''

"""
这是一个使用三双引号的多行注释
同样可以用于详细说明代码的相关信息
"""

x = "床前明月光，\
疑似地上霜，\
举头望明月，\
低头思故乡。"

print("这是一个"，
      "分行的"
      "例子")

a = 10;b=20;print(a+b)
# 同一行书写多个语句会使代码的可读性大大降低

import 模块名

# 获取用户输入的姓名
name = input("Please enter your name: ")
print(f"Hello, {name}!")

# 获取用户输入的整数
age_str = input("Please enter your age: ")
age = int(age_str)  # 将字符串转换为整数
print(f"Next year, you will be {age + 1} years old.")

# 获取用户输入的浮点数
height_str = input("Please enter your height (in meters): ")
height = float(height_str)  # 将字符串转换为浮点数
print(f"Your height in centimeters is {height * 100} cm.")

# 打印字符串
print("Hello, World!")
# 打印数字
print(123)
# 打印多个值，用逗号分隔，默认会用空格连接
print("The answer is", 42)

name = "Alice"
age = 25
print("My name is %s and I am %d years old." % (name, age))

num = 13.231
print("设置宽度为10，精度为2的数据：%10.2f"%num)
#运行结果为：设置宽度为10，精度为2的数据：     13.23

name = "Bob"
age = 30
print("My name is {} and I am {} years old.".format(name, age))

name = "Charlie"
age = 35
print(f"My name is {name} and I am {age} years old.")

# 正整数
positive_integer = 10
# 负整数
negative_integer = -20

# 普通浮点数
float_number = 3.14
# 科学计数法表示的浮点数
scientific_float = 1.23e-4  # 相当于 1.23 * 10^(-4)

complex_number = 2 + 3j

# 单引号字符串
single_quoted_string = 'Hello, World!'
# 双引号字符串
double_quoted_string = "Python is great"
# 三引号字符串，常用于多行字符串
multi_line_string = '''This is a
multi-line
string.'''

is_valid = True
has_error = False

result = None

numbers = [1, 2, 3, 4, 5]
mixed_list = [1, 'apple', True]

point = (3, 4)
single_element_tuple = (1,)  # 只有一个元素的元组需要在元素后面加逗号

fruits = {'apple', 'banana', 'cherry'}

person = {'name': 'John', 'age': 30, 'city': 'New York'}

# 给变量赋值
name = "Alice"  # 字符串类型
age = 25  # 整数类型
height = 1.65  # 浮点数类型
is_student = True  # 布尔类型

x = 10
print(x)  # 输出: 10
x = 20
print(x)  # 输出: 20

# 定义常量
PI = 3.14159
MAX_USERS = 100

PI = 3.14159
# 不建议这样做，但 Python 不会阻止
PI = 3.2  
print(PI)  # 输出: 3.2

num = 10
print(type(num))  # <class 'int'>

f_num = 3.14
print(type(f_num))  # <class 'float'>

c_num = 2 + 3j
print(type(c_num))  # <class 'complex'>

s = "Hello, World!"
print(type(s))  # <class 'str'>

lst = [1, 2, 'a']
print(type(lst))  # <class 'list'>

tup = (1, 2, 'a')
print(type(tup))  # <class 'tuple'>

dic = {'name': 'Alice', 'age': 20}
print(type(dic))  # <class 'dict'>

s1 = {1, 2, 3}
print(type(s1))  # <class 'set'>

fs = frozenset([1, 2, 3])
print(type(fs))  # <class 'frozenset'>

b = True
print(type(b))  # <class 'bool'>

s = "Hello, World!"
# 正向索引
print(s[0])  # 输出 'H'
print(s[7])  # 输出 'W'

# 负向索引
print(s[-1])  # 输出 '!'
print(s[-6])  # 输出 'W'

s1 = "Hello"
s2 = " World!"
s3 = s1 + s2
print(s3)  # 输出 'Hello World!'

s = "abc"
s_repeated = s * 3
print(s_repeated)  # 输出 'abcabcabc'

s = "Hello, World!"
# 提取从索引 0 到索引 4 的子字符串
print(s[0:5])  # 输出 'Hello'

# 省略 start，默认从 0 开始
print(s[:5])  # 输出 'Hello'

# 省略 stop，默认到字符串末尾
print(s[7:])  # 输出 'World!'

# 使用负索引
print(s[-6:-1])  # 输出 'World'

# 使用步长
print(s[::2])  # 输出 'Hlo ol!'

s = "hello world"
print(s.find("world"))  # 输出: 6

s = "hello world, world"
print(s.rfind("world"))  # 输出: 13

s = "hello world"
try:
    print(s.index("world"))  # 输出: 6
except ValueError:
    print("Substring not found")

s = "hello world, world"
try:
    print(s.rindex("world"))  # 输出: 13
except ValueError:
    print("Substring not found")

s = "hello world"
print(s.replace("world", "python"))  # 输出: hello python

s = "hello"
s_upper = s.upper()
print(s_upper)  # 输出 'HELLO'

s = "HELLO"
s_lower = s.lower()
print(s_lower)  # 输出 'hello'

s = "hello world"
s_title = s.title()
print(s_title)  # 输出 'Hello World'

s = "  hello  "
s_stripped = s.strip()
print(s_stripped)  # 输出 'hello'

s = "hello,world,python"
print(s.split(","))  # 输出: ['hello', 'world', 'python']

s = "hello,world,python"
print(s.rsplit(",", 1))  # 输出: ['hello,world', 'python']

s = "hello\nworld\npython"
print(s.splitlines())  # 输出: ['hello', 'world', 'python']

words = ["hello", "world", "python"]
print(", ".join(words))  # 输出: hello, world, python

s = "Hello, World!"
print(s.startswith("Hello"))  # 输出 True

s = "Hello, World!"
print(s.endswith("World!"))  # 输出 True

s = "Hello"
print(s.isalpha())  # 输出 True

s = "123"
print(s.isdigit())  # 输出 True

s = "hello123"
print(s.isalnum())  # 输出: True

s = "   "
print(s.isspace())  # 输出: True

# 浮点数转整数，直接截断小数部分
num1 = int(3.14)  
print(num1)  # 3

# 字符串转整数，字符串必须是合法的整数表示
num2 = int('10')  
print(num2)  # 10

# 整数转浮点数
f1 = float(10)  
print(f1)  # 10.0

# 字符串转浮点数，字符串必须是合法的数字表示
f2 = float('3.14')  
print(f2)  # 3.14

s1 = str(10)
print(s1)  # '10'

s2 = str([1, 2, 3])
print(s2)  # '[1, 2, 3]'

lst1 = list('abc')
print(lst1)  # ['a', 'b', 'c']

lst2 = list((1, 2, 3))
print(lst2)  # [1, 2, 3]

tup1 = tuple([1, 2, 3])
print(tup1)  # (1, 2, 3)

tup2 = tuple('abc')
print(tup2)  # ('a', 'b', 'c')

s1 = set([1, 2, 2, 3])
print(s1)  # {1, 2, 3}

s2 = set('abc')
print(s2)  # {'a', 'b', 'c'}

fs = frozenset([1, 2, 3])
print(fs)  # frozenset({1, 2, 3})

# 以下值转换为布尔值为False
print(bool(0))  # False
print(bool(0.0))  # False
print(bool(''))  # False
print(bool([]))  # False
print(bool(()))  # False
print(bool({}))  # False
print(bool(None))  # False

# 其他值转换为布尔值为True
print(bool(1))  # True
print(bool('a'))  # True
print(bool([1]))  # True

# 从包含键值对元组的列表创建字典
dic = dict([('name', 'Alice'), ('age', 20)])
print(dic)  # {'name': 'Alice', 'age': 20}