Python中打包和拆包的流程详解

python
# 打包成元组
a = 1, 2, 3
print(a)   # (1, 2, 3)
print(type(a))  # <class 'tuple'>

python
# 拆包元组
x, y, z = (1, 2, 3)
print(x, y, z)   # 1 2 3

python
# 列表拆包
lst = [10, 20, 30]
a, b, c = lst
print(a, b, c)   # 10 20 30

# 字符串拆包
s = "ABC"
x, y, z = s
print(x, y, z)   # A B C

python
# * 收集剩余元素为列表
first, *rest = [1, 2, 3, 4]
print(first)   # 1
print(rest)    # [2, 3, 4]

# 中间收集
first, *middle, last = [1, 2, 3, 4, 5]
print(first)   # 1
print(middle)  # [2, 3, 4]
print(last)    # 5

# 忽略不需要的元素（通常用 _ 占位）
_, second, _ = [10, 20, 30]
print(second)  # 20

python
def get_stats(numbers):
    return min(numbers), max(numbers), sum(numbers) / len(numbers)

result = get_stats([1,2,3,4,5])
print(result)   # (1, 5, 3.0)

# 拆包接收
min_val, max_val, avg = get_stats([1,2,3,4,5])
print(min_val, max_val, avg)   # 1 5 3.0

python
def show_args(*args, **kwargs):
    print("位置参数打包为元组:", args)
    print("关键字参数打包为字典:", kwargs)

show_args(1, 2, 3, name="Alice", age=25)
# 位置参数打包为元组: (1, 2, 3)
# 关键字参数打包为字典: {'name': 'Alice', 'age': 25}

python
def add(a, b, c):
    return a + b + c

# 列表拆包为位置参数
nums = [1, 2, 3]
print(add(*nums))   # 6

# 字典拆包为关键字参数
kwargs = {'a': 10, 'b': 20, 'c': 30}
print(add(**kwargs))   # 60

python
dict1 = {'a': 1, 'b': 2}
dict2 = {'c': 3, 'd': 4}
merged = {**dict1, **dict2}
print(merged)   # {'a': 1, 'b': 2, 'c': 3, 'd': 4}

python
defaults = {'host': 'localhost', 'port': 8080}
config = {'port': 9090, 'debug': True}
final = {**defaults, **config}
print(final)   # {'host': 'localhost', 'port': 9090, 'debug': True}

python
def greet(name, age):
    print(f"{name} is {age} years old.")

person = {'name': 'Bob', 'age': 30}
greet(**person)   # Bob is 30 years old.

python
# 嵌套元组拆包
data = (1, (2, 3))
a, (b, c) = data
print(a, b, c)   # 1 2 3

# 嵌套列表拆包
lst = [10, [20, 30]]
x, [y, z] = lst
print(x, y, z)   # 10 20 30

python
t = (1, 2, 3, 4)
first, *rest = t
print(type(rest))   # <class 'list'>

python
# 错误示例
# a, *b, *c = [1,2,3,4,5]   # SyntaxError

python
first, *rest = []
# ValueError: not enough values to unpack (expected at least 1, got 0)
# 需要至少一个变量来匹配

python
a, b = 5, 10
a, b = b, a
print(a, b)   # 10 5

python
path = "/home/user/docs/file.txt"
folders, filename = path.rsplit('/', 1)
print(folders)   # /home/user/docs
print(filename)  # file.txt

python
def logger(func):
    def wrapper(*args, **kwargs):
        print(f"调用 {func.__name__} 参数: args={args}, kwargs={kwargs}")
        return func(*args, **kwargs)
    return wrapper

@logger
def add(a, b):
    return a + b

add(3, 5)   # 调用 add 参数: args=(3, 5), kwargs={}

python
list1 = [1, 2]
list2 = [3, 4]
merged = [*list1, *list2]
print(merged)   # [1, 2, 3, 4]

python
def get_data():
    return 1, 2, 3, 4, 5

a, b, *_ = get_data()   # 只取前两个
print(a, b)   # 1 2