CODEWITHSUNDEEP
pythoniteratorrangeenumerate
apostofes
apostofes

Reputation: 3693

Difference in iterating through range vs enumerate

next(range(2))

gives error,

TypeError: 'range' object is not an iterator

but,

next(iter(range(2)))

works, and gives the output 0

but,

next(enumerate('a'))

works, and gives the output

(0, 'a')

and,

next(iter(enumerate('a')))

also does the same.

shouldn't both work in a similar way, what is the reason for this difference?

Upvotes: 0

Views: 439

Answers (1)

tdelaney
tdelaney

Reputation: 77347

A range object is an iterable that can be used many times. Each time you create an iterator for range,you get a new range_iterator object that starts from the beginning of the range and is unaffected by other iterators created on the same object.

>>> r = range(2)
>>> type(r)
<class 'range'>
>>> type(iter(r))
<class 'range_iterator'>
>>> iter(r) is r
False

A enumerate object is an iterator. It will iterate through the contained sequence one time. Any new iterators created on the enumeration are in fact the same iterator object and using one affects any other copies you may have.

>>> e = enumerate('a')
>>> type(e)
<class 'enumerate'>
>>> type(iter(e))
<class 'enumerate'>
>>> iter(e) is e
True

In short, enumerate is the same as range_iterator, not range.

Upvotes: 3

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