Iterator
Python da iterator obyektlar __iter__ va __next__ metodlari orqali amalga oshiriladi. Iterator obyektni iterable tiplar list, tuple, dict, str va boshqa, iter() built_in metodi orqali yaratamiz va elementlarni olishda next() metodidan foydalanamiz.
Manba: Codingninjas
my_list = [2, 4, 8, 16, 32]
iterator = iter(my_list)
print(next(iterator)) # 2
print(next(iterator)) # 4
print(next(iterator)) # 8
print(next(iterator)) # 16
print(next(iterator)) # 32
print(next(iterator)) # StopIteration
Iterator oxirgi elementidan keyin next ishlatilsa StopIteration xatolik qaytaradi.
Xuddi shuni for loop orqali amalga oshiramiz.
my_list = [2, 4, 8, 16, 32]
for item in my_list:
print(item)
# 2
# 4
# 8
# 16
# 32
Iterator obyekt elementlarini for loop orqali ham olishimiz mumkin.
my_list = [2, 4, 8, 16, 32]
iterator = iter(my_list)
for item in iterator:
print(item)
# 2
# 4
# 8
# 16
# 32
__iter__ va __next__ metodlarni o'zgartirgan holda iterator obyekt yaratamiz.
class PowTwo:
def __init__(self, limit=0):
self.limit = limit
def __iter__(self):
self.n = 1
return self
def __next__(self):
if self.n <= self.limit:
pow_number = 2 ** self.n
self.n += 1
return pow_number
else:
raise StopIteration
numbers = PowTwo(5)
iterator = iter(numbers)
print(next(iterator)) # 2
print(next(iterator)) # 4
print(next(iterator)) # 8
print(next(iterator)) # 16
print(next(iterator)) # 32
print(next(iterator)) # StopIteration
iter() va next() built_in metodlar ishlatganimizda class da yozilgan __iter__ va __next__ metodlarga murojaat qilinadi.
numbers = PowTwo(5)
iterator = numbers.__iter__()
print(iterator.__next__()) # 2
print(iterator.__next__()) # 4
print(iterator.__next__()) # 8
print(iterator.__next__()) # 16
print(iterator.__next__()) # 32
print(iterator.__next__()) # StopIteration
Generator
Manba: Medium
Python da generator funksiya oddiy funksiyadek bo'ladi, faqat yield kalit so'zi orqali qiymat qaytariladi.
def generator():
yield 1
yield 2
yield 3
for value in generator():
print(value)
# 1
# 2
# 3
Generator funksiya generator obyekt qaytaradi.
print(generator())
# <generator object generator at 0x7f1af486aea0>
Generator obyekt dan iterator sifatida foydalanib next() orqali ham qiymatlarni olishimiz mumkin.
my_generator = generator()
print(next(my_generator)) # 1
print(next(my_generator)) # 2
print(next(my_generator)) # 3
print(next(my_generator)) # StopIteration
Nima uchun funksiyada return o'rniga yield ishlatilyapti?
return funksiyada berilgan qiymatni qaytaradi, yield esa ketma-ketlikni qaytarib yuboradi. Biz funksiyada butun bir ketma-ketlik xotirada saqlamasdan qaytarmoqchi bo'lsak yield foydalanishimiz kerak.
Raqamlar ro'yxatidan ularning kvadratlarini qaytaradigan generator funksiya yaratib ko'ramiz.
def square(nums):
for num in nums:
yield num ** 2
numbers = [1, 2, 3]
generator = square(numbers)
print(next(generator)) # 1
print(next(generator)) # 4
print(next(generator)) # 9
print(next(generator)) # StopIteration
Generator funksiya orqali qaytariladigan ketma-ketlikni sum() va boshqa iterable qabul qiladigan funksiyalar orqali ishlatsak ham bo'ladi.
numbers = [1, 2, 3]
sum_of_square_numbers = sum(square(numbers))
print(sum_of_square_numbers) # 14
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