inconsistent behavior of tuple without parenthesis between tuple and list comprehensions and for statement

[luoxzhg]

Bug report

tuple without parenthesis in for statement is allowed

for i in 1,2,3: print(i)

output

1
2

but in list comprehensions, it is SyntaxError

[i for i in 1,2,3]

output

  File "<stdin>", line 1
    [i for i in 1, 2, 3]
                 ^
SyntaxError: invalid syntax

tuple comprehensions is same as this.

Your environment

• CPython versions tested on: '3.11.2 (main, Feb 16 2023, 03:15:23) [Clang 14.0.0 (clang-1400.0.29.202)]'
• Operating system and architecture:macos 12.6.3 x64

[corona10]

I think that it can be a conflict with the following case.

https://github.com/python/cpython/blob/4f5774f648eafd1a7076ecf9af9629fb81baa363/Lib/test/test_grammar.py#L1797

[iritkatriel]

This is only a bug if the behaviour contradicts the documentation. Does it?

[iritkatriel]

CC @pablogsal

[pablogsal]

I think this is ambiguous and that's why we don't allow it. I will investigate it with more care to see what we can do

[pablogsal]

Ah if I recall correctly this is to not make it inconsistent with generator comprehensions where using them directly in a function call is ambiguous:

foo(x for (x,y) in X, Y)