nonlocal والحالة القابلة للتغيير

قراءة المتغيرات المحيطة وكتابتها

def outer():
    count = 0
    def inner():
        return count
    return inner()
print(outer())

مأزق الإسناد

def outer():
    count = 0
    def bump():
        count = count + 1
    try:
        bump()
    except UnboundLocalError as e:
        print('Error:', e)
outer()

الكلمة المفتاحية nonlocal

def outer():
    count = 0
    def bump():
        nonlocal count
        count += 1
    bump()
    bump()
    return count
print(outer())

إغلاق العداد

def make_counter():
    count = 0
    def increment():
        nonlocal count
        count += 1
        return count
    return increment
c = make_counter()
print(c())
print(c())
print(c())

عدادات مستقلة

def make_counter():
    count = 0
    def inc():
        nonlocal count
        count += 1
        return count
    return inc
a = make_counter()
b = make_counter()
print(a(), a(), b())

nonlocal مقابل global

total = 0
def add_global(n):
    global total
    total += n
add_global(5)
add_global(3)
print(total)

حالة قابلة للتغيير دون nonlocal

def make_logger():
    history = []
    def log(msg):
        history.append(msg)
        return history
    return log
log = make_logger()
log('start')
print(log('stop'))

المجمِّع التراكمي

def make_accumulator():
    total = 0
    def add(n):
        nonlocal total
        total += n
        return total
    return add
acc = make_accumulator()
print(acc(10))
print(acc(5))
print(acc(100))

تبديل بسيط

def make_toggle():
    on = False
    def toggle():
        nonlocal on
        on = not on
        return on
    return toggle
t = make_toggle()
print(t(), t(), t())

إعادة ضبط الحالة

def make_bank():
    balance = 0
    def deposit(n):
        nonlocal balance
        balance += n
        return balance
    def reset():
        nonlocal balance
        balance = 0
        return balance
    return deposit, reset
deposit, reset = make_bank()
print(deposit(50))
print(reset())

يحتاج nonlocal إلى متغير موجود

def outer():
    value = 'set'
    def inner():
        nonlocal value
        value = 'changed'
    inner()
    return value
print(outer())

تحقق سريع

مراجعة: nonlocal والحالة القابلة للتغيير

def make_counter():
    n = 0
    def inc():
        nonlocal n
        n += 1
        return n
    return inc
c = make_counter()
print(c(), c())