Python编程基础概念

    x = 10

    name = "Alice"
    is_student = True

    # 重复的值 比较麻烦
    
    # 不使用变量
    print("树木丛生，百草丰茂")
    print("树木丛生，百草丰茂")
    print("树木丛生，百草丰茂")
    print("树木丛生，百草丰茂")
    
    
    # 使用变量
    # 变量的格式 ： 变量的名称 = 变量的值
    word = "树木丛生，百草丰茂aaa"
    
    print(word)
    print(word)
    print(word)
    print(word)

    # 标识符由字母、下划线和数字组成，且数字不能开头。
    # a_1_$ = 1
    # print(a_1_$)
    
    # 严格区分大小写。
    # Animal = 1
    # print(animal)
    
    # 不能使用关键字。
    # for = 1
    # print(for)

    a = 10
    b = -5

    c = 3.5
    d = -2.8

    e = ,
    f = -2 + 3j

    # Python 2
    b = 100000000000000000000000000000000000000000000000L  # 在 Python 2 中，L 表示 long 类型
    print(b)  # 输出一个长整数
    
    # 转换为 Python 3
    b = 100000000000000000000000000000000000000000000000  # 在 Python 3 中，L 后缀不再需要
    print(b)  # 输出同样的结果，但现在是 int 类型

    greeting = "Hello, World!"
    name = 'Alice'

    full_name = "John" + " " + "Doe"

    age = 30
    message = f"Name: {name}, Age: {age}"

    is_true = True
    is_false = False

    result = (x > 0) and (y < 5)

    numbers = [1, 2, 3]
    mixed = [1, "two", 3.0, True]
    i = [1, 2, 3]
    j = ["apple", "banana", "cherry"]

    k = (1, 2, 3)
    l = ("apple", "banana", "cherry")
    coordinates = (4, 0.25)
    colors = ("red", "green", "blue")

    r = range(1, 10)  # 生成 1 到 9 的整数序列
    for i in r:
    print(i)

    for i in range(2, 10, 3):
    print(i)

    person = {"name": "Alice", "age": 25}
    scores = {1: "one", 2: "two"}

    unique_numbers = {1, 2, 3}
    fruits = {"apple", "banana", "cherry"}

    value = None

    # 整型
    a = 10
    b = -5
    
    # 浮点型
    c = 3.14
    d = -2.8
    
    # 复数
    e = 3 + 4j
    f = -2 + 3j
    
    # 字符串
    greeting = "Hello, World!"
    name = 'Alice'
    
    # 布尔型
    is_true = True
    is_false = False
    
    # 列表
    numbers = [1, 2, 3]
    mixed = [1, "two", 3.0, True]
    
    # 元组
    coordinates = (4, 0.25)
    colors = ("red", "green", "blue")
    
    # 范围
    r = range(1, 10)
    for i in r:
    print(i)
    
    # 字典
    person = {"name": "Alice", "age": 25}
    scores = {1: "one", 2: "two"}
    
    # 集合
    unique_numbers = {1, 2, 3}
    fruits = {"apple", "banana", "cherry"}
    
    # None 类型
    value = None
    
    # 字符串操作
    full_name = "John" + " " + "Doe"
    age = 30
    message = f"Name: {name}, Age: {age}"
    
    # 字典操作
    print(person["name"])  # 输出: Alice
    person["age"] = 26  # 修改字典中的值
    person["email"] = "alice@example.com"  # 添加新的键值对
    print(person)  # 输出: {'name': 'Alice', 'age': 26, 'email': 'alice@example.com'}
    
    # 集合操作
    set1 = {1, 2, 3}
    set2 = {2, 3, 4}
    union = set1.union(set2)  # 并集
    intersection = set1.intersection(set2)  # 交集
    difference = set1.difference(set2)  # 差集
    print(union)  # 输出: {1, 2, 3, 4}
    print(intersection)  # 输出: {2, 3}
    print(difference)  # 输出: {1}

    # len
    s = 'china'
    print(len(s))
    
    s1 = 'china'
    print(s1.find('a'))
    
    s2 = 'china'
    print(s2.startswith('h'))
    print(s2.endswith('n'))
    
    s3 = 'artfdhdrfsaa'
    print(s3.count('a'))
    
    s4 = 'cdgdsdseea'
    print(s4.replace('d','o'))
    
    s5 = '1#@#2#3#4#856'
    print(s5.split('#'))
    
    s6 = 'china'
    print(s6.upper())
    
    s7 = 'CHINA'
    print(s7.lower())
    
    s8 = '     ar  e  '
    print(len(s8))
    print(len(s8.strip()))
    
    s9 = 'a'
    print(s9.join('hello'))

    # append 在末尾添加元素
    food_list = ['铁锅','大鹅','五花肉']
    print(food_list)
    
    food_list.append('酸菜')
    print(food_list)
    
    # insert 在指定位置插入元素
    char_list = ['a','b','c']
    print(char_list)
    
    # insert(index, object) 在指定位置index前插入元素object
    char_list.insert(1,'h')
    print(char_list)
    
    # extend 合并两个列表
    num_list = [1,2,3]
    num1_list = [4,5,6]
    
    num_list.extend(num1_list)
    print(num_list)

    city_list = ['北京','上海','武汉','西安']
    print(city_list)
    
    city_list[3] = '大连'
    print(city_list)

    # in 判断某一个元素，是否在列表中
    city_list = ['北京','上海','武汉','西安']
    
    # 判断在控制台输入的数据，是否在列表中
    city = input('请输入现在待的城市：')
    
    if city in city_list:
    print('呆着呢')
    else:
    print('玩去了')
    
    
    
    # not in 判断某一个元素，是否不在列表中
    food_list = ['酸菜','大鹅','五花肉']
    
    # 判断在控制台输入的数据，是否不在列表中
    food = input('请输入食材：')
    
    if food not in food_list:
    print('不吃')
    else:
    print('吃美了')

    a_list = [1,2,3,4,5,6]
    print(a_list)
    
    del a_list[2]
    print(a_list)

    food_list = ['酸菜','大鹅','五花肉']
    print(food_list)
    food_list.pop()
    print(food_list)

    food_list = ['酸菜','大鹅','五花肉','火锅']
    food_list.remove('五花肉')
    print(food_list)

    a_tuple = (a,2,3,4,5)
    print(a_tuple[0])
    print(a_tuple[2])
    
    # a_tuple[3] = 5
    # print(a_tuple)
    
    a_list = [sa,3,5,df,3,y]
    a_list[2] = 246
    print(a_list)
    
    b_tuple = (11,)
    print(type(b_tuple))

    s = 'Hello World!'
    print(s)
    print(s[4])  # o 字符串里的第4个元素
    print(s[3:7])  # lo W 包含下标 3，不含下标 7
    print(s[1:])  # ello World! 从下标为1开始，取出 后面所有的元素（没有结束位）
    print(s[:4])  # Hell 从起始位置开始，取到 下标为4的前一个元素（不包括结束位本身）
    print(s[1:5:2])  # el 从下标为1开始，取到下标为5的前一个元素，步长为2（不包括结束位本身）

    使用key查找数据，还可以使用get来获取数据`
    person = {'name':'武器' ,'age':23 }
    print(person['name'])
    print(person['age'])
    
    print(person.get('name'))
    print(person.get('age'))
    
    # print(info['sex']) # 获取不存在的key，会发生异常
    print(info.get('sex'))  # 获取不存在的key，获取到空的内容，不会出现异常
    print(info.get('sex', '男'))  # 获取不存在的key, 可以提供一个默认值。

    person = {'name':'张三' ,'age':23 }
    print(person)
    person['name'] = '法外'
    print(person)

    person = {'name':'牛奶' }
    print(person)
    person['age']=18
    person['name'] = '大团购'
    print(person)

    person = {'name':'牛奶','age': 12 }
    print(person)
    del person['age']
    print(person)
    
    person1 = {'name':'牛奶','age': 12 }
    del person1
    print(person1)
    
    person2 = {'name':'牛奶','age': 12 }
    person2.clear()
    print(person2)

    person = {'name':'牛奶','age': 12,'sex':'nan' }
    
    for test in person.keys():
    print(test)

    person = {'name':'牛奶','age': 12,'sex':'nan' }
    
    for value in person.values():
    print(value)

    person = {'name':'牛奶','age': 12,'sex':'nan' }
    
    for item in person.items():
    print(item)

    person = {'name':'牛奶','age': 12,'sex':'nan' }
    
    for key,value in person.items():
    print(key,value)

    print(int("123")) # 123 将字符串转换成为整数
    print(int(123.78)) # 123 将浮点数转换成为整数
    print(int(True)) # 1 布尔值True转换成为整数是 1
    print(int(False)) # 0 布尔值False转换成为整数是 0
    
    # 转换为整型
    # str --> int
    a = '123'
    print(type(a))
    # 将字符串转换为整数
    b = int(a)
    print(type(b))
    
    # float --> int
    c = 1.23
    print(type(c))
    # 将float转换为整数，返回的是小数点前面的数据
    d = int(c)
    print(d)
    print(type(d))
    
    
    # boolean --> int
    e = True
    print(type(e))
    f = int(e)
    print(f)
    print(type(f))

    # 123.456 和 12ab 字符串，都包含非法字符，不能被转换成为整数，会报错
    print(int("123.456"))
    print(int("12ab"))

    f1 = float("12.34")
    print(f1) # 12.34
    print(type(f1)) # float 将字符串的 "12.34" 转换成为浮点数 12.34
    f2 = float(23)
    print(f2) # 23.0
    print(type(f2)) # float 将整数转换成为了浮点数

    # 转换为字符串
    a = 80
    print(type(a))
    # 强制类型转换为字符串
    b = str(a)
    print(b)
    print(type(b))
    
    str1 = str(45)
    str2 = str(34.56)
    str3 = str(True)
    print(type(str1),type(str2),type(str3))

    # 如果对非0的整数进行bool类型的转换，那么全都是True
    e = -1
    print(type(e))
    f = bool(e)
    print(f)
    
    print(bool(''))
    print(bool(""))
    print(bool(0))
    print(bool({}))
    print(bool([]))
    print(bool(()))

    a = 10
    b = 0.25
    
    # 加法
    print(a + b)  # 10.25
    
    # 减法
    print(a - b)  # 9.75
    
    # 乘法
    print(a * b)  # 2.5
    
    # 除法
    print(a / b)  # 40.0
    
    # 整除
    print(a // b)  # 40
    
    # 取模
    print(a % b)  # 0.˜
    
    # 幂
    print(a ** 2)  # 100

    a = "hello"
    b = " "
    c = "world"
    print(a + b + c)

    a = "hello"
    b = 12
    c = "world"
    print(a + b + c)

    a = "hello"
    b = 10
    print(a*b)

    x = 5
    y = 10
    
    # 等于
    print(x == y)  # False
    
    # 不等于
    print(x != y)  # True
    
    # 大于
    print(x > y)  # False
    
    # 小于
    print(x < y)  # True
    
    # 大于等于
    print(x >= y)  # False
    
    # 小于等于
    print(x <= y)  # True

    p = True
    q = False
    
    # 逻辑与
    print(p and q)  # False
    
    # 逻辑或
    print(p or q)  # True
    
    # 逻辑非
    print(not p)  # False

    m = 60  # 二进制 0011 1100
    n = 13  # 二进制 0000 1101
    
    # 按位与
    print(m & n)  # 12 (二进制 0000 1100)
    
    # 按位或
    print(m | n)  # 61 (二进制 0011 1101)
    
    # 按位异或
    print(m ^ n)  # 49 (二进制 0011 0001)
    
    # 按位取反
    print(~m)  # -61 (取决于机器的位宽)
    
    # 左移
    print(m << 2)  # 240 (二进制 1111 0000)
    
    # 右移
    print(m >> 2)  # 15 (二进制 0000 1111)

    i = 10
    
    # 加法赋值
    i += 3  # 相当于 i = i + 3
    print(i)  # 13
    
    # 乘法赋值
    i *= 2  # 相当于 i = i 
    print(i)  # 26
    
    # 取模赋值
    i %= 5  # 相当于 i = i % 5
    print(i)  # 1

    my_list = [1, 2, 3, 4, 5]
    
    # 检查成员
    print(3 in my_list)  # True
    print(6 not in my_list)  # True

    x = [1, 2, 3]
    y = [1, 2, 3]
    z = x
    
    # 检查身份
    print(x is z)  # True
    print(x is y)  # False，尽管 x 和 y 有相同的值，但它们不是同一个对象
    print(x is not y)  # True

    age = 20
    
    if age < 18:
    print("你是未成年人。")
    elif age >= 18 and age < 60:
    print("你是成年人。")
    else:
    print("你是老年人。")

    # 遍历列表
    fruits = ["apple", "banana", "cherry"]
    for fruit in fruits:
    print(fruit)
    
    # 使用 range() 函数
    for i in range(5):  # 0 到 4
    print(i)

    count = 0
    while count < 5:
    print(count)
    count += 1  # count = count + 1

    for i in range(10):
    if i == 5:
        break  # 当 i 等于 5 时退出循环
    print(i)

    for i in range(10):
    if i % 2 == 0:  # 如果 i 是偶数
        continue  # 跳过当前循环的剩余部分
    print(i)  # 只打印奇数

    def my_function():
    pass  # 占位符，将来可能会在这里写代码
    
    for letter in 'Python':
    if letter == 'h':
        pass  # 不做任何事情，只是保持语法结构
    print('当前字母:', letter)

    try:
    result = 10 / 0
    except ZeroDivisionError:
    print("除数不能为零！")
    else:
    print("结果是:", result)
    finally:
    print("无论是否发生异常，都会执行这里。")

    # 使用 with 语句打开文件
    with open('example.txt', 'r') as file:
    content = file.read()
    print(content)
    # 文件在 with 语句结束时自动关闭

    def divide(a, b):
    assert b != 0, "除数不能为零"
    return a / b
    
    # 如果 b 为 0，将会抛出 AssertionError
    result = divide(10, 0)

    def get_day_name(day):
    match day:
        case 1:
            return "周一"
        case 2:
            return "周二"
        case 3:
            return "周三"
        case 4:
            return "周四"
        case 5:
            return "周五"
        case 6:
            return "周六"
        case 7:
            return "周日"
        case _:
            return "无效的天数"
    
    print(get_day_name(3))  # 输出: 周三

    def simple_generator():
    yield 1
    yield 2
    yield 3
    
    gen = simple_generator()
    for value in gen:
    print(value)
    # 输出:
    # 1
    # 2
    # 3

    # 使用 lambda 创建一个简单的函数
    square = lambda x: x * x
    print(square(5))  # 输出: 25

    # 创建一个平方数的列表
    squares = [x * x for x in range(10)]
    print(squares)  # 输出: [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

    def add(a, b):
    return a + b
    
    result = add(3, 4)
    print(result)  # 输出: 7

    # 导入整个模块
    import math
    
    # 从模块中导入特定的函数或类
    from datetime import datetime
    
    # 使用导入的模块和函数
    print(math.sqrt(16))  # 输出: 4.0
    print(datetime.now())  # 输出当前日期和时间

    my_list = [1, 2, 3]
    del my_list[0]  # 删除第一个元素
    print(my_list)  # 输出: [2, 3]
    
    # 删除整个列表
    del my_list
    # 再次访问 my_list 会导致 NameError

    def 函数名():
    	代码

    # 定义函数
    def f1():
    print("欢迎光临")
    print("两位")
    
    # 调用函数
    f1()

    # 定义函数
    def sum(a,b):
    c = a + b
    print(c)
    
    # 位置参数  按照位置一一对应的关系来传递参数
    sum(100,200)
    
    
    # 关键字传参
    sum(b= 300,a= 200)

    # 返回值的关键字是return，存在函数中
    def buy():
    return '冰激凌'
    
    # 使用一个变量接收函数的返回值
    food = buy()
    print(food)
    
    
    def sum(a,b):
    c = a + b
    return c
    
    a = sum(125,68)
    print(a)

    def f1():
    a = 1
    print(a)
    
    f1()
    print(a)

    a = 1
    print(a)
    def f1():
    print(a)
    
    f1()

    print("Hello, World!")

    name = input("请输入你的名字: ")
    print(f"你好, {name}!")

    my_list = [1, 2, 3]
    print(len(my_list))  # 输出: 3

    my_list = list((1, 2, 3))
    my_tuple = tuple([1, 2, 3])
    my_set = set([1, 2, ¾, 3])  # 注意这里修正了½为¾，因为½不是有效的Python语法
    my_dict = dict(name="Alice", age=30)
    print(my_list, my_tuple, my_set, my_dict)

    x = int("10")
    y = float("3.14")
    z = str(100)
    w = bool(0)  # False
    print(x, y, z, w)

    numbers = [1, 2, 3, 4, 5]
    print(max(numbers))  # 输出: 5
    print(min(numbers))  # 输出: 1

    numbers = [1, 2, 3, 4, 5]
    print(sum(numbers))  # 输出: 15

    x = -10
    print(abs(x))  # 输出: 10

    x = 3.14159
    print(round(x, 2))  # 输出: 3.14

    fruits = ["apple", "banana", "cherry"]
    for index, fruit in enumerate(fruits):
    print(index, fruit)

    names = ["Alice", "Bob", "Charlie"]
    ages = [25, 30, 35]
    for name, age in zip(names, ages):
    print(f"{name} is {age} years old.")

    for i in range(5):
    print(i)  # 输出: 0, 1, 2, 3, 4

    print(all([True, True, True]))  # 输出: True
    print(any([False, False, True]))  # 输出: True

    numbers = [1, 2, 3, 4, 5]
    even_numbers = filter(lambda x: x % 2 == 0, numbers)
    print(list(even_numbers))  # 输出: [2, 4]

    numbers = [1, 2, 3, 4, 5]
    squared = map(lambda x: x ** 2, numbers)
    print(list(squared))  # 输出: [1, 4, 9, 16, 25]

    from functools import reduce
    numbers = [1, 2, 3, 4, 5]
    product = reduce(lambda x, y: x * y, numbers)
    print(product)  # 输出: 120

    with open('example.txt', 'r') as file:
    content = file.read()
    print(content)

    help(print)

    # 这是一个单行注释

    """
    这是一个
    多行注释
    """

    # 单行注释
    print("国庆出去玩")  # 单行注释

    # 多行注释
    '''
    东临碣石，
    以观沧海。
    水何澹澹，
    山岛竦峙。
    print("树木丛生，百草丰茂")
    print("秋风萧瑟，洪波涌起")
    '''

    '''
    这是多行注释，用三个单引号
    这是多行注释，用三个单引号 
    这是多行注释，用三个单引号
    '''
    print("Hello, World!")

    """
    这是多行注释（字符串），用三个双引号
    这是多行注释（字符串），用三个双引号 
    这是多行注释（字符串），用三个双引号
    """
    print("Hello, World!")

    print("Hello, World!")

    user_input = input("请输入您的名字: ")

    print('hello')

    print('%s' % 'hello world')  # 字符串输出
    hello world
    #就是将非字符串%后面的字符串替换成'%s'

    >>> print('{0:b}'.format(3))
    11
    >>> print('{:c}'.format(20))
    
    >>> print('{:d}'.format(20))
    20
    >>> print('{:o}'.format(20))
    24
    >>> print('{:x}'.format(20))
    14
    >>> print('{:e}'.format(20))
    2.000000e+01
    >>> print('{:g}'.format(20.1))
    20.1
    >>> print('{:f}'.format(20))
    20.000000
    >>> print('{:n}'.format(20))
    20
    >>> print('{:%}'.format(20))
    2000.000000%

    name = 'Bertram'
    age = 30
    print(f"hello,{name},you are {age}")

    password = input("请输入密码:")
    print('您刚刚输入的密码是:%s' % password)

    try:
    # 可能引发异常的代码
    except ExceptionType as e:
    # 处理异常的代码
    finally:
    # 无论是否发生异常都会执行的代码

    # 变量
    x = 10
    y = 3.14
    name = "Alice"
    is_student = True
    
    # 数据类型
    numbers = [1, 2, 3]
    coordinates = (4, 0.25)
    person = {"name": "Bob", "age": 30}
    fruits = {"apple", "banana", "cherry"}
    
    # 运算符
    result = x + y
    is_greater = x > y
    logical_and = (x > 0) and (y < 5)
    
    # 控制流语句
    if x > y:
    print("x is greater than y")
    elif x < y:
    print("x is less than y")
    else:
    print("x is equal to y")
    
    for fruit in fruits:
    print(fruit)
    
    i = 0
    while i < 5:
    print(i)
    i += 1
    
    # 函数
    def greet(name):
    return f"Hello, {name}!"
    
    message = greet("Alice")
    print(message)
    
    # 输入输出
    user_input = input("请输入您的名字: ")
    print(f"您好, {user_input}!")
    
    # 异常处理
    try:
    number = int(input("请输入一个数字: "))
    result = 10 / number
    print(f"结果是: {result}")
    except ValueError:
    print("输入的不是有效的数字")
    except ZeroDivisionError:
    print("除数不能为零")
    finally:
    print("程序结束")