range(2,3) in range(1,5) should return True (sub-sequence test) or raise TypeError.

[simonltwick]

Feature or enhancement

Proposal:

This came up as I was looking for overlapping ranges.

The expression range(2,3) in range(1,5) is accepted as valid Python but always returns false.

I was expecting it to return True. However I see that from the documentation the strict definition is "True if it's equal to an element in the range, else False", so this is working as per the documentation, although it is confusing.

I see that note 1 in the documentation ([(https://docs.python.org/3/library/stdtypes.html#typesseq)]) states that some specialised elements (string, bytes, buffer) have implemented subsequence testing, e.g. "gg" in "eggs".

I'm hoping that range can have this implemented so that range(2,3) in range(1,5) returns True.
If not, perhaps it should raise a TypeError or ValueError to prevent that type of operation?

Thank you for considering this suggestion, and acknowledgement to Stefano Rivera who suggested I submit this as an upstream request.
Simon Lambourn.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

[StanFromIreland]

True if it's equal to an element in the range, else False

"element" is the key part here, the object range(2,3) is not in the elements of range(1,5), which are: 1, 2, 3, 4.

If not, perhaps it should raise a TypeError or ValueError to prevent that type of operation?

This would unnecessarily break backwards compatibility IMO.

Maybe the docs could note this, but I don't think it is necessary.

[serhiy-storchaka]

Note that [2] in [1, 2, 3, 4] is False. range is just a special optimized representation for an immutable list of consequent integers.

For strings and string-like objects in is defined differently, but this is exception.