Description

hauntsaninja

opened on Apr 13, 2023

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I had a coworker slightly confused about the following warning, since None is a literal and is not None is idiomatic:

>>> 'a' is not None
<stdin>:1: SyntaxWarning: "is not" with a literal. Did you mean "!="?
True

I think this would be better as:

>>> 'a' is not None
<stdin>:1: SyntaxWarning: "is not" with str literal. Did you mean "!="?
True

Linked PRs

• gh-103492: Clarify SyntaxWarning with literal comparison #103493

Activity

1. hauntsaninja

   added

   type-featureA feature request or enhancementA feature request or enhancement

   on Apr 13, 2023
2. hauntsaninja

   added 2 commits that reference this issue on Apr 13, 2023

   pythongh-103492: Clarify SyntaxWarning with literal comparison

   5247c04

   Merge branch 'main' into pythongh-103492

   41c9ad9
3. terryjreedy commented on Apr 13, 2023

   

   terryjreedy

   on Apr 13, 2023

   Member

   More actions

   https://docs.python.org/3/reference/lexical_analysis.html#literals

   Literals are notations for constant values of some built-in types.
   In particular bytes, strings, and numbers are discussed in the following.
   https://docs.python.org/3/reference/expressions.html#literals is more specific.
   Python supports string and bytes literals and various numeric literals:
   Evaluation of a literal yields an object of the given type (string, bytes, integer, floating point number, complex number) with the given value.

   None is a constant, but not a 'literal' as defined in the sections above. This is only to say that the current message is not really ambiguous. Still, the added detail may help some.

   https://docs.python.org/3/reference/expressions.html#parenthesized-forms
   A tuple is a 'parenthesized form' that is either empty or has at least 1 comma. A constant tuple is not really a literal, but testing I see that one is already called a 'literal'.

   The test changes look good; can't review the c code.
4. hauntsaninja

   added a commit that references this issue on Apr 24, 2023

   gh-103492: Clarify SyntaxWarning with literal comparison (#103493)

   ae25855
5. carljm

   added 2 commits that reference this issue on Apr 24, 2023

   Merge branch 'main' into superopt

   dbe1665

   Merge branch 'superopt' into superopt_spec

   793a69a
6. hauntsaninja

   closed this as completedon Apr 26, 2023

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