Python 内置了大量实用的函数，无需导入任何模块即可直接使用
输入输出：print(), input()
类型转换：int(), str(), list() 等
数学运算：abs(), sum(), min(), max() 等
序列操作：len(), sorted(), zip(), enumerate() 等
函数式编程：map(), filter(), any(), all() 等
对象操作：type(), isinstance(), getattr() 等
编译执行：eval(), exec(), compile() 等






一、基本输入输出函数

1. print() - 输出函数
# 基本用法
print("Hello, World!")  # Hello, World!

# 多个参数
print("Name:", "Alice", "Age:", 25)  # Name: Alice Age: 25

# 指定分隔符
print("2023", "12", "15", sep="-")  # 2023-12-15

# 指定结束符
print("Line 1", end=" ")
print("Line 2")  # Line 1 Line 2

# 格式化输出
name = "Bob"
age = 30
print(f"{name} is {age} years old")  # Bob is 30 years old


2. input() - 输入函数

# 基本用法
name = input("Enter your name: ")
print(f"Hello, {name}!")

# 输入数值（需要类型转换）
age = int(input("Enter your age: "))
height = float(input("Enter your height (m): "))
print(f"Age: {age}, Height: {height}m")



二、类型转换函数

3. int(), float(), str(), bool()

# 整数转换
print(int(3.14))      # 3
print(int("42"))      # 42
print(int("101", 2))  # 5 (二进制转十进制)

# 浮点数转换
print(float(10))      # 10.0
print(float("3.14"))  # 3.14

# 字符串转换
print(str(100))       # "100"
print(str(3.14))      # "3.14"
print(str([1, 2, 3])) # "[1, 2, 3]"

# 布尔转换
print(bool(0))        # False
print(bool(1))        # True
print(bool(""))       # False
print(bool("Hello"))  # True
print(bool([]))       # False
print(bool([1, 2]))   # True


4. list(), tuple(), set(), dict()

# 列表转换
print(list("abc"))          # ['a', 'b', 'c']
print(list((1, 2, 3)))      # [1, 2, 3]
print(list({1, 2, 3}))      # [1, 2, 3]

# 元组转换
print(tuple([1, 2, 3]))     # (1, 2, 3)
print(tuple("abc"))         # ('a', 'b', 'c')

# 集合转换（自动去重）
print(set([1, 2, 2, 3, 3])) # {1, 2, 3}
print(set("hello"))         # {'h', 'e', 'l', 'o'}

# 字典转换
items = [("a", 1), ("b", 2)]
print(dict(items))          # {'a': 1, 'b': 2}


三、数学运算函数

5. abs(), round(), divmod(), pow()
# 绝对值
print(abs(-10))      # 10
print(abs(3.14))     # 3.14

# 四舍五入
print(round(3.14159, 2))  # 3.14
print(round(3.5))         # 4
print(round(2.5))         # 2 (银行家舍入法)

# 商和余数
print(divmod(10, 3))      # (3, 1)
print(divmod(10.5, 3))    # (3.0, 1.5)

# 幂运算
print(pow(2, 3))          # 8
print(pow(2, 3, 3))       # 2 (2^3 % 3)


6. sum(), min(), max()

# 求和
numbers = [1, 2, 3, 4, 5]
print(sum(numbers))               # 15
print(sum(numbers, 10))           # 25 (从10开始累加)

# 最小值/最大值
print(min(3, 1, 4, 1, 5))         # 1
print(max([3, 1, 4, 1, 5]))       # 5

# 使用key参数
words = ["apple", "banana", "cherry", "date"]
print(min(words, key=len))        # date
print(max(words, key=len))        # banana


四、序列操作函数

7. len(), sorted(), reversed(), enumerate()


# 长度
print(len("Hello"))        # 5
print(len([1, 2, 3]))      # 3
print(len({"a": 1, "b": 2})) # 2

# 排序
nums = [3, 1, 4, 1, 5, 9]
print(sorted(nums))                   # [1, 1, 3, 4, 5, 9]
print(sorted(nums, reverse=True))     # [9, 5, 4, 3, 1, 1]

# 自定义排序
words = ["apple", "Banana", "cherry", "Date"]
print(sorted(words))                  # ['Banana', 'Date', 'apple', 'cherry']
print(sorted(words, key=str.lower))   # ['apple', 'Banana', 'cherry', 'Date']

# 反转
nums = [1, 2, 3, 4, 5]
rev = reversed(nums)
print(list(rev))                      # [5, 4, 3, 2, 1]

# 枚举
fruits = ["apple", "banana", "cherry"]
for i, fruit in enumerate(fruits):
    print(f"{i}: {fruit}")

# 0: apple
# 1: banana
# 2: cherry

# 指定起始索引
for i, fruit in enumerate(fruits, start=1):
    print(f"{i}: {fruit}")


8. zip(), range()

# zip函数 - 合并多个序列
names = ["Alice", "Bob", "Charlie"]
ages = [25, 30, 35]
scores = [85, 90, 95]

for name, age, score in zip(names, ages, scores):
    print(f"{name}: {age} years, score: {score}")

# 转成字典
print(dict(zip(names, ages)))  # {'Alice': 25, 'Bob': 30, 'Charlie': 35}

# range函数 - 生成数字序列
print(list(range(5)))          # [0, 1, 2, 3, 4]
print(list(range(1, 6)))       # [1, 2, 3, 4, 5]
print(list(range(0, 10, 2)))   # [0, 2, 4, 6, 8]
print(list(range(10, 0, -1)))  # [10, 9, 8, 7, 6, 5, 4, 3, 2, 1]


五、迭代器和生成器函数

9. iter(), next(), filter(), map()
# iter和next
numbers = [1, 2, 3]
it = iter(numbers)
print(next(it))  # 1
print(next(it))  # 2
print(next(it))  # 3
# print(next(it))  # StopIteration异常


# filter函数 - 过滤序列
def is_even(n):
    return n % 2 == 0

nums = [1, 2, 3, 4, 5, 6]
evens = filter(is_even, nums)
print(list(evens))  # [2, 4, 6]

# 使用lambda表达式
evens = filter(lambda x: x % 2 == 0, nums)
print(list(evens))  # [2, 4, 6]

# map函数 - 对序列每个元素应用函数
def square(x):
    return x ** 2

squares = map(square, nums)
print(list(squares))  # [1, 4, 9, 16, 25, 36]

# 多个序列
a = [1, 2, 3]
b = [10, 20, 30]
result = map(lambda x, y: x + y, a, b)
print(list(result))  # [11, 22, 33]


六、对象操作函数


10. id(), type(), isinstance(), issubclass()

# 对象标识
x = [1, 2, 3]
y = [1, 2, 3]
print(id(x))  # 内存地址（每次运行不同）
print(id(y))  # 与x不同
print(x is y) # False

# 类型检查
print(type(42))              # <class 'int'>
print(type("Hello"))         # <class 'str'>
print(type([1, 2, 3]))       # <class 'list'>

# 类型判断
print(isinstance(42, int))   # True
print(isinstance("Hello", (str, int)))  # True (str或int)

# 子类判断
class Animal:
    pass

class Dog(Animal):
    pass

print(issubclass(Dog, Animal))  # True
print(issubclass(Dog, object))  # True

11. hasattr(), getattr(), setattr(), delattr()

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

p = Person("Alice", 25)

# 检查属性
print(hasattr(p, "name"))    # True
print(hasattr(p, "height"))  # False

# 获取属性
print(getattr(p, "name"))    # Alice
print(getattr(p, "height", "N/A"))  # N/A (默认值)

# 设置属性
setattr(p, "height", 170)
print(p.height)              # 170

# 删除属性
delattr(p, "height")
# print(p.height)            # AttributeError



七、作用域相关函数

12. globals(), locals()

x = 10  # 全局变量

def test():
    y = 20  # 局部变量
    print("局部变量:", locals())    # {'y': 20}
    print("全局变量:", globals().get('x'))  # 10

test()
print("全局命名空间:", globals().keys())


八、编译和执行函数

13. eval(), exec(), compile()

# eval - 计算表达式
x = 10
result = eval("x * 2 + 5")
print(result)  # 25

# exec - 执行代码
code = """
for i in range(3):
    print(f"Number: {i}")
"""
exec(code)

# compile - 编译代码
code_str = "print('Hello, World!')"
compiled = compile(code_str, '<string>', 'exec')
exec(compiled)



九、其他实用函数

14. open() - 文件操作

# 写入文件
with open("example.txt", "w") as f:
    f.write("Hello, World!\n")
    f.write("This is a test file.\n")

# 读取文件
with open("example.txt", "r") as f:
    content = f.read()
    print(content)

# 逐行读取
with open("example.txt", "r") as f:
    for line in f:
        print(line.strip())


15. help(), dir()

# 获取帮助
help(print)  # 显示print函数的帮助信息

# 查看对象属性
print(dir([]))      # 查看列表的方法
print(dir("hello")) # 查看字符串的方法

# 查看内置函数
import builtins
print(dir(builtins))


16. any(), all()

# any - 任意元素为True则返回True
print(any([False, False, True]))    # True
print(any([0, 0, 0]))               # False

# all - 所有元素为True则返回True
print(all([True, True, True]))      # True
print(all([1, 2, 0]))               # False


十、高级应用示例

综合示例：数据处理管道

# 使用多个内置函数处理数据
data = ["10", "20", "30", "40", "50"]

# 转换为整数，过滤大于25的数，计算平方
result = list(
    map(
        lambda x: x**2,
        filter(
            lambda x: x > 25,
            map(int, data)
        )
    )
)

print(result)  # [900, 1600, 2500]

# 更简洁的写法（使用列表推导式）
result = [x**2 for x in map(int, data) if x > 25]
print(result)  # [900, 1600, 2500]


综合示例：对象排序

# 复杂对象排序
students = [
    {"name": "Alice", "score": 85, "age": 20},
    {"name": "Bob", "score": 92, "age": 22},
    {"name": "Charlie", "score": 78, "age": 19},
    {"name": "David", "score": 92, "age": 21}
]

# 按分数降序，年龄升序排序
sorted_students = sorted(
    students,
    key=lambda x: (-x["score"], x["age"])
)

for student in sorted_students:
    print(student)