Python返回值与多返回值

return 语句将函数结果返回给调用者，Python 支持返回多个值。

return 语句

基本用法

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

result = add(3, 5)
print(result)  # 8

无 return 或空 return

def greet(name):
    print(f"Hello, {name}")

result = greet("Alice")
print(result)  # None

def process():
    return  # 等同于 return None

立即终止函数

def check_positive(n):
    if n < 0:
        return "negative"  # 立即终止
    return "positive"

print(check_positive(-5))  # negative
print(check_positive(5))   # positive

多返回值

返回多个值（实际是元组）

def get_info():
    name = "Alice"
    age = 25
    city = "Beijing"
    return name, age, city  # 返回元组

# 元组解包接收
n, a, c = get_info()
print(n, a, c)  # Alice 25 Beijing

# 整体接收
info = get_info()
print(info)     # ('Alice', 25, 'Beijing')
print(type(info))  # tuple

实际应用

计算统计值

def calculate_stats(numbers):
    return min(numbers), max(numbers), sum(numbers)

minimum, maximum, total = calculate_stats([1, 2, 3, 4, 5])
print(f"min={minimum}, max={maximum}, sum={total}")
# min=1, max=5, sum=15

分割字符串

def split_name(full_name):
    parts = full_name.split()
    return parts[0], parts[1] if len(parts) > 1 else ""

first, last = split_name("Alice Smith")
print(first, last)  # Alice Smith

查找索引

def find_item(items, target):
    if target in items:
        return items.index(target), True
    return -1, False

index, found = find_item([1, 2, 3], 2)
print(f"index={index}, found={found}")  # index=1, found=True

元组解包

基本解包

def get_coordinates():
    return 10, 20

x, y = get_coordinates()

扩展解包

def get_values():
    return 1, 2, 3, 4, 5

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

忽略某些返回值

def get_data():
    return "Alice", 25, "Beijing"

name, _, city = get_data()  # 用 _ 忽略 age
print(name, city)  # Alice Beijing

返回字典

当返回值较多时

def get_user_info():
    return {
        "name": "Alice",
        "age": 25,
        "city": "Beijing",
        "email": "alice@example.com"
    }

info = get_user_info()
print(info["name"])  # Alice

返回列表

返回多个结果集合

def find_even_and_odd(numbers):
    evens = [n for n in numbers if n % 2 == 0]
    odds = [n for n in numbers if n % 2 != 0]
    return evens, odds

even_list, odd_list = find_even_and_odd([1, 2, 3, 4, 5])
print(even_list)  # [2, 4]
print(odd_list)   # [1, 3, 5]

要点总结

1. return 将结果返回给调用者，立即终止函数
2. 无 return 或空 return 返回 None
3. 多返回值实际是元组，通过解包接收
4. 使用 _ 忽略不需要的返回值
5. 返回值较多时建议返回字典