[issue35077] Make TypeError message less ambiguous

[Karthikeyan Singaravelan]

Karthikeyan Singaravelan  added the comment:

https://bugs.python.org/issue44110 did some improvements to error message to 
include type.

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[issue35077] Make TypeError message less ambiguous

[coyot linden]

coyot linden  added the comment:

3.8 has come and gone, resubmitting this for 3.10

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versions: +Python 3.10 -Python 3.8

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[issue35077] Make TypeError message less ambiguous

[coyot linden]

coyot linden  added the comment:

Sure, this can wait to the next release. I don't see it as groundshatteringly 
;) urgent.

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[issue35077] Make TypeError message less ambiguous

[Terry J. Reedy]

Terry J. Reedy  added the comment:

Aside from the effort of making a change correct and consistent across our 
code, error message changes often breaks user code and tests that depend on the 
current wording.  So there must be sufficient benefit to overcome the cost.  
(The user breakage cost is why we nearly always wait for the next version to 
make such changes.)

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[issue35077] Make TypeError message less ambiguous

[coyot linden]

coyot linden  added the comment:

The problem I have with "So only the 'index of string' interpretation makes 
sense." is that by the time a developer has that understanding, they won't get 
this error. So it's fine and logical to say from the behind-the-scenes view 
that only sequences talk about indices, but that's not helpful to the confused 
developer who gets this message. The point of error messages should be to 
clearly indicate the problem and solution, not rely on the developer having a 
global understanding of error messages.

So, rather than defend the current practice, I ask if there are arguments 
against "X of Y". Is there some context in which that is confusing?

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[issue35077] Make TypeError message less ambiguous

[Terry J. Reedy]

Terry J. Reedy  added the comment:

I checked a bit.  All the 'index' entries in the index are about sequences.  
However, https://docs.python.org/3/reference/datamodel.html has this abstract 
(non-Python) description:

"Mappings
These represent finite sets of objects indexed by arbitrary index sets. The 
subscript notation a[k] selects the item indexed by k from the mapping a; ...
Dictionaries
These represent finite sets of objects indexed by nearly arbitrary 
values."

I personally would prefer 'keyed' or 'subscripted' and 'key'to prevent 
confusion.  The entry then switches to the usual Python term 'key'.

"The only types of values not acceptable as keys  ... a key’s hash value ... 
used for keys ..."

https://docs.python.org/3/library/stdtypes.html#mapping-types-dict uses 'index' 
once as a verb, otherwise uses 'key'.

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[issue35077] Make TypeError message less ambiguous

[Terry J. Reedy]

Terry J. Reedy  added the comment:

I have a mixed opinion of this.  On the one hand, 'string index', taken out of 
context, *is* ambiguous.  (In the context of the TypeError message, it took me 
a minute to see the string-index interpretation.)  On the other hand, dicts do 
not have indices.  They have keys.  So only the 'index of string' 
interpretation makes sense.

Is there anything in the docs that suggests that a mapping subscript can be 
called an 'index' in addition to 'key'?

It would be nicer if this TypeError message also included 'not x', but there 
may be an issue that the type x info is lost.

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nosy: +terry.reedy

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[issue35077] Make TypeError message less ambiguous

[coyot linden]

coyot linden  added the comment:

You're welcome. I filed against 3.5 because that's what I have in our env at 
the moment and I couldn't test and thus assert the issue in later versions. 

Happy to see the problem addressed more generally.

The abstraction of the problem is the ambiguity in English between nouns used 
as adjectives and their groupings: (noun phrase) versus (noun as 
adjective)(noun). Using "X of Y" rather than (XY) or (X)(Y) resolves the 
ambiguity.

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[issue35077] Make TypeError message less ambiguous

[Karthikeyan Singaravelan]

Karthikeyan Singaravelan  added the comment:

Thanks for the report. Error message changes are generally done on master and 
not back ported. I am removing 3.5 which is security fixes only mode and adding 
3.8 . There are other errors of similar format but indicate the wrong type in 
the error message like list indices.

$ ./python.exe
Python 3.8.0a0 (heads/bpo31177-dirty:19986202a8, Oct 26 2018, 22:19:23)
[Clang 7.0.2 (clang-700.1.81)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> [1]['1']
Traceback (most recent call last):
  File "", line 1, in 
TypeError: list indices must be integers or slices, not str

I think we should also assert the error message in test_slice 
(Lib/test/string_tests.py) if there is a change.

Thanks Serhiy, I was about to add Raymond too who might have thoughts on the 
wording :)

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nosy: +xtreak
versions: +Python 3.8 -Python 3.5

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[issue35077] Make TypeError message less ambiguous

[Serhiy Storchaka]

Change by Serhiy Storchaka :


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nosy: +rhettinger

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[issue35077] Make TypeError message less ambiguous

[శ్రీనివాస్ రెడ్డి తాటిపర్తి]

Change by Srinivas  Reddy Thatiparthy(శ్రీనివాస్ రెడ్డి తాటిపర్తి) 
:


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keywords: +patch
pull_requests: +9464
stage:  -> patch review

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[issue35077] Make TypeError message less ambiguous

[శ్రీనివాస్ రెడ్డి తాటిపర్తి]

Srinivas  Reddy Thatiparthy(శ్రీనివాస్ రెడ్డి తాటిపర్తి) 
 added the comment:

+1. 

In my early days of python programming i was confused of this message.

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nosy: +thatiparthy

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[issue35077] Make TypeError message less ambiguous

[coyot linden]

New submission from coyot linden :

The TypeError message:

TypeError: string indices must be integers

is ambiguously written. While some may understand the intent, others will read 
it as confusingly saying that strings must be integers since dicts among other 
things do have string indices.  Suggest changing the message to:

TypeError: indices of strings must be integers

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messages: 328565
nosy: coyot
priority: normal
severity: normal
status: open
title: Make TypeError message less ambiguous
type: enhancement
versions: Python 3.5

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