skip first two elements in an enumeration -- python

Question

This is not what I want from enumerate:

>>> seasons = ['Spring', 'summer', 'fall', 'winter']

>>> list(enumerate(seasons, start =2))

[(2, 'Spring'), (3, 'summer'), (4, 'fall'), (5, 'winter')]

This IS the functionality I want from enumerate:

 >>> list(enumerate(seasons, start =2))
[(2, 'fall'), (3, 'winter')]

See the difference? The first one just says, "fine I'll call your 0th element 2 if you really want me to"

The second one says, "I understand that you just want to begin the loop at the second index, much like range(2, len(seasons)) would do"

Is there no way to do this simply with enumerate?

No, not with enumerate, enumerate always yields something for each item in the iterable you give it. — RemcoGerlich, Apr 07 '16 at 14:28

idjaw · Accepted Answer · 2016-04-07T14:32:44.393

14

Why not just slice the first two elements?

print(list(enumerate(seasons[2:], start=2)))

Output:

[(2, 'fall'), (3, 'winter')]

To understand what is going on with enumerate and the start. Try iterating over it to see what it outputs:

for i, v in enumerate(seasons, start=2):
    print(i, v)

As you can see your i, which simply increments along iterating through your seasons list is what starts at 2. But each value in the list is actually from the start of your list. This just further proves that start does not have anything to do with the actual starting point of your list iteration.

edited Apr 07 '16 at 14:32

answered Apr 07 '16 at 14:26

idjaw

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While this was my first attempt as well and works for lists, it won't work for any `iterable`, i.e. it won't work on the ones that are not `subscriptable`. On the other hand, the answer by @awesoon actually works for any `iterable`. – penelope May 21 '19 at 11:23

score 10 · Answer 2 · answered Apr 07 '16 at 14:34

10

You could use itertools.islice in order to take a slice of an iterable:

In [9]: from itertools import islice

In [10]: list(islice(enumerate(seasons), 2, None))
Out[10]: [(2, 'fall'), (3, 'winter')]

answered Apr 07 '16 at 14:34

awesoon

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This, thank you. Your solution works for any `iterable` - and I'm honestly surprised this question/answer isn't getting more attention. – penelope May 21 '19 at 11:24

skip first two elements in an enumeration -- python

2 Answers2