Python中nonlocal和global的区别及闭包使用

count = 10
def modify_count():
    global count
    count = 20
    print(count)

modify_count()  # 输出 20
print(count)    # 输出 20，全局变量count已经被修改

def outer():
    num = 5
    def inner():
        nonlocal num
        num = 10
        print(num)
    inner()
    print(num)

outer()  
# 输出 10
# 输出 10，因为内层函数通过nonlocal修改了外层函数的num变量

def counter():
    count = 0
    def increment():
        nonlocal count
        count += 1
        return count
    return increment

count_func = counter()
print(count_func())  # 输出 1
print(count_func())  # 输出 2
print(count_func())  # 输出 3

def accumulator(initial_value=0):
    def accumulate(num):
        nonlocal initial_value
        initial_value += num
        return initial_value
    return accumulate

acc = accumulator(5)
print(acc(3))  # 输出 8，初始值5加上传入的3
print(acc(2))  # 输出 10，基于上一次结果8再加上传入的2

def tax_calculator(tax_rate):
    def calculate_tax(amount):
        return amount * tax_rate
    return calculate_tax

calculate_sales_tax = tax_calculator(0.08)  # 8% 的销售税
calculate_income_tax = tax_calculator(0.2)  # 20% 的所得税
print(calculate_sales_tax(100))  # 输出 8
print(calculate_income_tax(1000))  # 输出 200