Ben Finney wrote:
Steven D'Aprano <st...@pearwood.info> writes:
As far as I can see, in practice, people talk about obj[i] as the item
at index i, not the item at subscript i -- the term "subscript" in
this context seems to be rare to non-existent except for the error
message.
Presumably, the same people would also call ‘obj[i]’ the item at *key*
‘i’, if ‘obj’ is a dictionary. For an object that supports neither
indexes nor keys, though, how is Python to know which the user meant?
It's a single operation as far as the parser is concerned, so there
needs to be a single term for it. That term is “subscript”.
Your point about the awkward word “unsubscriptable” is well-taken,
though. Perhaps a simple improvement to the message wording:
>>> foo = 3
>>> foo[6]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'int' object does not support subscripts
>>> foo['spam']
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'int' object does not support subscripts
It's called a 'subscript' because conventional mathematical notation
uses subscripting. Newbies might be acquainted with the term 'index'
from books, where the 'value' is non-numeric. It's a bit unfortunate
that dicts have keys+value instead of index+value! :-)
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