Description

JelleZijlstra

opened on Feb 28, 2024

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Feature or enhancement

Proposal:

I often use ast.parse in the terminal to explore what the AST looks like:

>>> ast.parse("x = 3")
<ast.Module object at 0x105450b50>

But I have to remember to use ast.dump() to get useful output:

>>> ast.dump(ast.parse("x = 3"))
"Module(body=[Assign(targets=[Name(id='x', ctx=Store())], value=Constant(value=3))], type_ignores=[])"

It would be nice if the default repr() of AST nodes was more like the output of ast.dump(), so it's easier to see at a glance how it works.

One concern would be around the size of the output:

>>> from pathlib import Path
>>> import typing
>>> typing_py = Path(typing.__file__).read_text()
>>> len(ast.dump(ast.parse(typing_py)))
304244

As a middle ground, we could limit the depth of the AST provided in the repr(), e.g. to 2 levels, and also the number of list elements provided.

The repr() of a module's AST might then look something like:

Module(body=[Expr(value=Constant(...)), ..., Assign(targets=[Name(...)], value=Constant(...))], type_ignores=[])

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-116022: Improve repr() of AST nodes #117046

Reacted by Daniël van Noord, Tomas R. and Alex Waygood

Activity

1. JelleZijlstra

   added

   type-featureA feature request or enhancementA feature request or enhancement

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   topic-parser

   on Feb 28, 2024
2. tomasr8 commented on Mar 10, 2024

   

   tomasr8

   on Mar 10, 2024

   Member

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   This is something that would be useful for me as well since I also sometimes poke around the AST 😄

   Were you planning to implement this yourself or do you think I could give it a try? Looking at the code, it'll probably have to be implemented in C since that's where the base AST type is defined.
3. JelleZijlstra commented on Mar 10, 2024

   

   JelleZijlstra

   on Mar 10, 2024

   MemberAuthor

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   I will do it eventually if no one else gets to it but haven't started yet. You're welcome to start working on it! This might need changes to asdl_c.py which is the Python code that generates the C code for the AST.

   Reacted by Tomas R.
4. JelleZijlstra

   added a commit that references this issue on Sep 18, 2024

   gh-116022: Improve `repr()` of AST nodes (#117046)

   21d2a9a
5. JelleZijlstra

   closed this as completedin #117046on Sep 18, 2024
6. savannahostrowski

   added a commit that references this issue on Sep 22, 2024

   pythongh-116022: Improve `repr()` of AST nodes (python#117046)

   491004a

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