一文带你掌握5个鲜为人知的Python内置函数

# any(): 只要有一个为True，就返回True
numbers = [0, 2, 4, 6, 8]
has_odd = any(n % 2 != 0 for n in numbers)  # False

# all(): 所有元素都为True，才返回True
all_positive = all(n > 0 for n in numbers)  # False (0不是正数)

# 传统写法
def validate_user(user):
    if not user.get('name'):
        return False
    if not user.get('email'):
        return False
    if not user.get('age'):
        return False
    return True

# 使用 all() - 简洁明了
def validate_user(user):
    required_fields = ['name', 'email', 'age']
    return all(user.get(field) for field in required_fields)

# 检查用户是否拥有任一管理员权限
permissions = ['read', 'write', 'delete']
admin_permissions = ['admin', 'superuser', 'delete']
is_admin = any(perm in admin_permissions for perm in permissions)

fruits = ['apple', 'banana', 'cherry']

# 传统写法
index = 0
for fruit in fruits:
    print(f"{index}: {fruit}")
    index += 1

# 使用 enumerate() - 优雅简洁
for index, fruit in enumerate(fruits):
    print(f"{index}: {fruit}")

# 从1开始编号（比如显示排名）
for rank, player in enumerate(players, start=1):
    print(f"第{rank}名: {player}")

names = ['Alice', 'Bob', 'Charlie']
scores = [95, 87, 92]

for i, (name, score) in enumerate(zip(names, scores)):
    print(f"学生{i+1}: {name} - {score}分")

# 找出列表中所有偶数的索引
numbers = [1, 4, 7, 8, 10, 3, 6]
even_indices = [i for i, n in enumerate(numbers) if n % 2 == 0]
# 结果: [1, 3, 4, 6]

names = ['Alice', 'Bob', 'Charlie']
ages = [25, 30, 35]
cities = ['Beijing', 'Shanghai', 'Shenzhen']

for name, age, city in zip(names, ages, cities):
    print(f"{name}, {age}岁, 来自{city}")

keys = ['name', 'age', 'email']
values = ['Alice', 25, 'alice@example.com']
user_dict = dict(zip(keys, values))
# {'name': 'Alice', 'age': 25, 'email': 'alice@example.com'}

matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]
transposed = list(zip(*matrix))
# [(1, 4, 7), (2, 5, 8), (3, 6, 9)]

numbers = [1, 2, 3, 4, 5]
# 计算相邻元素的差值
differences = [b - a for a, b in zip(numbers, numbers[1:])]
# [1, 1, 1, 1]

quotient, remainder = divmod(17, 5)
# quotient = 3, remainder = 2

def seconds_to_time(seconds):
    minutes, secs = divmod(seconds, 60)
    hours, mins = divmod(minutes, 60)
    return f"{hours:02d}:{mins:02d}:{secs:02d}"

print(seconds_to_time(3665))  # "01:01:05"

def calculate_pagination(total_items, items_per_page):
    total_pages, extra = divmod(total_items, items_per_page)
    if extra > 0:
        total_pages += 1
    return total_pages

pages = calculate_pagination(97, 10)  # 10页

def convert_cents(total_cents):
    dollars, cents = divmod(total_cents, 100)
    return f"${dollars}.{cents:02d}"

print(convert_cents(1234))  # "$12.34"

# 传统方法（两次运算）
q = a // b
r = a % b

# divmod（一次运算）
q, r = divmod(a, b)  # 更快！

class User:
    def __init__(self):
        self.name = "Alice"
        self.age = 25

user = User()

# getattr(): 动态获取属性
name = getattr(user, 'name')  # "Alice"
# 提供默认值避免AttributeError
email = getattr(user, 'email', 'N/A')  # "N/A"

# setattr(): 动态设置属性
setattr(user, 'email', 'alice@example.com')

# hasattr(): 检查属性是否存在
if hasattr(user, 'phone'):
    print(user.phone)

class Config:
    def __init__(self):
        self.debug = False
        self.database = 'sqlite'
        self.port = 8000

def update_config(config, updates):
    """根据字典批量更新配置"""
    for key, value in updates.items():
        if hasattr(config, key):
            setattr(config, key, value)
        else:
            print(f"警告: 未知配置项 {key}")

config = Config()
update_config(config, {'debug': True, 'port': 9000, 'unknown': 'value'})

class Product:
    def __init__(self, **kwargs):
        # 动态设置所有传入的属性
        for key, value in kwargs.items():
            setattr(self, key, value)

product = Product(name="Laptop", price=999, stock=50)
print(product.name)  # "Laptop"

def safe_get_nested(obj, path, default=None):
    """安全地获取嵌套属性，例如 'user.profile.email'"""
    keys = path.split('.')
    for key in keys:
        if hasattr(obj, key):
            obj = getattr(obj, key)
        else:
            return default
    return obj

# 使用示例
value = safe_get_nested(user, 'profile.settings.theme', 'light')

def export_to_dict(obj, fields):
    """将对象的指定字段导出为字典"""
    return {
        field: getattr(obj, field, None) 
        for field in fields
    }

user_data = export_to_dict(user, ['name', 'age', 'email'])