Итератори и генератори
„ Програмиране с Python“, ФМИ
11.03.2010
Програма
Цар, мустаци, градове, сума на прости числа, случайни хора
Итератор
next(обект)- при липсва на повече ни дава грешка
- можем да циклим по него
f = open('cities')
next(f)
for line in f:
print(line)
Генератори
def biscuits(pack):
pack.open()
while not pack.empty():
biscuit = pack.take_out()
yield biscuit
for biscuit in biscuits(favori):
if biscuit.examine():
biscuit.eat()
else:
biscuit.throw_away()
Прости числа с генератор
def primes(limit, number_modifier=None):
if number_modifier is None: number_modifier = lambda x: x
for number in range(2, limit + 1):
if all([number % divisor for divisor in range(2, number)]):
yield number_modifier(number)
Играчка
p = primes(10, lambda x: x + 1)
next(p)
for prime in p:
print(prime)
list(p)
list(primes(10, lambda x: x + 1))
Generator expressions
primes = [number for number in range(100) if all([number % divisor for divisor in range(2, number)])]
primes = (number for number in range(100) if all(number % divisor for divisor in range(2, number)))
def primes(limit, number_modifier=None):
if number_modifier is None: number_modifier = lambda x: x
for number in range(2, limit + 1):
if all((number % divisor for divisor in range(2, number))):
yield number_modifier(number)
вградени функции
map()filter()zip()list(),tuple()- itertools
Още въпроси?
- Страница на курса: http://fmi.py-bg.net/
- Форуми на курса: http://fmi.py-bg.net/topics