Hi Pythonistas!
Today we are learning how to slice an iterator properly?. Common mistakes we are making while slicing an iterator is first converting the iterator to a normal list and slicing the list. Issue with this approach is that the memory efficiency of the generator cannot be used. This can be done using itertools. Let us learn by an example.
Normal way
In [2]: a = range(100)
In [3]: a
Out[3]: range(0, 100)
In [4]: sliced_array = list(a)[10:25]
In [5]: sliced_array
Out[5]: [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24]
In [6]:Correct way
In [11]: import itertools
In [12]: a
Out[12]: range(0, 100)
In [13]: sliced_generator = itertools.islice(a, 10, 25)
In [14]: sliced_generator
Out[14]: <itertools.islice at 0x7be1df65ba60>
In [15]: for i in sliced_generator:
...: print(i)
...:
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
In [16]:We can see that in the second example output is generator. So it will be memory efficient. I hope you have learned something from this post. Please share your valuable suggestions with afsal@parseltongue.co.in