python - Return mini batch of items from generator -


i'm trying create class wraps generator function, can obtain items generator in batches of predefined size.

i.e. if had list of 10 random numbers , specified mini batch size of 2 i'd 5 tuples of 2 numbers.

i wrote following wrapper class generator function hoping job:

import random  class multiple_lottery_draws(object):     def __init__(self, num_draws):         self.num_draws = num_draws         print("initialized % draws"%self.num_draws)      def my_lottery(self):         # returns 9 numbers between 1 , 100         in range(10):             yield random.randint(1, 100)          # returns 10th number between 1000 , 2000         yield random.randint(1000,2000)      def __iter__(self):         data = []         in range(self.num_draws):             data.append(next(iter(self.my_lottery())))         yield data  two_draws = multiple_lottery_draws(2)

however, although generator works fine, 

for in two_draws.my_lottery(): print # prints: 52,12,61,67,30,78,84,90,69,31,1069

if try obtain mini-batches wrapper class 1 item

for in two_draws: print # prints: [74, 95]

what doing wrong?

you call yield once. try this:

def __iter__(self):     data = []      in self.my_lottery():         data.append(i)          if len(data) == self.num_draws:             yield data             data = []      if data:         yield data

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