Iterator Kustom

Pemrograman Berorientasi Objek Tingkat Menengah di Python

Jake Roach

Data Engineer

Iterator

Kelas yang memungkinkan traversal koleksi atau aliran data, dan mengembalikan satu item tiap kali

Mirip list, tuple, tetapi berperilaku berbeda
Menavigasi, mentransformasi, menghasilkan
Di-loop dengan for
Fungsi next()

Protokol iterator...

# Collection
chuck = NameIterator("Charles Carmicheal")
for letter in chuck:
    print(letter)

C
h
u
...

# Data stream
fun_game = DiceGame(rolls=3)
next(fun_game)  # ... and so on

Protokol iterator

__iter__()

Mengembalikan sebuah iterator, di sini referensi ke dirinya
... return self

__next__()

Mengembalikan nilai berikutnya dalam koleksi atau aliran data
Tempat iterasi, transformasi, dan generasi terjadi

Keduanya __iter__() dan __next__() harus didefinisikan agar suatu kelas dianggap iterator!

Contoh iterator

class CoinFlips:
    def __init__(self, number_of_flips):
        self.number_of_flips = number_of_flips  # Store the total number of flips
        self.counter = 0

    def __iter__(self):
        return self  # Return a reference of the iterator

    # Flip the next coin, return the output
    def __next__(self):
        if self.counter < self.number_of_flips:
            self.counter += 1
            return random.choice(["H", "T"])

Menggunakan contoh iterator

three_flips = CoinFlips(3)

# Flip the coin three times
next(three_flips)
next(three_flips)
next(three_flips)

H
H
T

Melakukan loop pada iterator

three_flips = CoinFlips(3)

# Now, try to loop through every element of the iterator
for flip in three_flips:
    print(flip)

T
H
T
None
None
None
...

StopIteration

...
    def __next__(self):
        # Only do this if the coin hasn't been flipped "number_of_flips" times
        if self.counter < self.number_of_flips:
            self.counter += 1
            return random.choice(["H", "T"])

        else:  # Otherwise, stop execution with StopIteration
            raise StopIteration

Menandai akhir koleksi/aliran data
Mencegah loop tak hingga
Mudah ditangani

Melakukan loop pada iterator

three_flips = CoinFlips(3)

# Now, try to loop through every element of the iterator
for flip in three_flips:
    print(flip)

H
T
H

Menangani pengecualian StopIteration

while True:
    try:
        next(three_flips)  # Pull the next element of three_flips

    # Catch a stop iteration exception
    except StopIteration:
        print("Completed all coin flips!")
        break

H
H
H
Completed all coin flips!

Ayo berlatih!

Pemrograman Berorientasi Objek Tingkat Menengah di Python