CODEWITHSUNDEEP
pythonpython-3.xindexingslice
Joe
Joe

Reputation: 547

Can [:1] be used in place of [0]?

I was reading the source code of the Python xml.etree.ElementTree module (https://github.com/python/cpython/blob/master/Lib/xml/etree/ElementTree.py) and I came across an interesting use of slices. The authors wrote the following code:

prefix = text[:1]

Which as far as I can tell is identical to:

try:
    prefix = text[0]
except IndexError:
    prefix = text

Are these code snippets identical? What are the benefits and detriments of using [:1] in place of [0]?

Upvotes: 0

Views: 70

Answers (4)

iperelivskiy
iperelivskiy

Reputation: 3591

If your question is scoped by string usage only, then yes – they are identical. You get benefit from less code, but second snippet is more pythonic and explicit.

Upvotes: 0

Fred Larson
Fred Larson

Reputation: 62083

One other difference: text[0] results in an exception if text is an empty list, while text[:1] returns an empty list. Similarly, indexing an empty string will give you an exception while slicing returns an empty string.

Upvotes: 2

hd1
hd1

Reputation: 34677

Slices -- [:1] -- return a list, whereas [0] returns an atom.

Upvotes: 0

Querenker
Querenker

Reputation: 2365

The difference is in the output format:

a[:1] returns a list with the first element. While a[0] returns the first element.

>>> a = [1, 2, 3, 4, 5, 6]
>>> a[:1]
[1]
>>> a[0]
1

Upvotes: 2

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