[New-bugs-announce] [issue39981] Default values for AST Nodes

[Batuhan Taskaya]

New submission from Batuhan Taskaya <batuhanosmantaskaya at gmail.com>:

For omitting some defaults, @serhiy.storchaka already added support to initialize some ast nodes with some default values (optional fields). An example;
>>> ast.Constant().kind is None
True

This isn't exactly a default value, but some kind of class attribute. I think we can push this one step further and initialize all kinds of default values (both optionals and sequences). An example;
>>> func = ast.FunctionDef("easy_func", ast.arguments(), body=[ast.Pass()])
>>> func = ast.fix_missing_locations(func)
>>> exec(compile(ast.Module(body=[func]), "<stdin>", "exec"))
>>> easy_func()

compared to this (other way around, compiler gives errors so does most of the ast based tool, including ast.unparser)
>>> func = ast.FunctionDef("easy_func", ast.arguments(posonlyargs=[], args=[], kwonlyargs=[], kw_defaults=[], defaults=[]), decorator_list=[], body=[ast.Pass()])
>>> func = ast.fix_missing_locations(func)
>>> exec(compile(ast.Module(body=[func], type_ignores=[]), "<stdin>", "exec"))
>>> easy_func()

----------
components: Library (Lib)
messages: 364355
nosy: BTaskaya, benjamin.peterson, pablogsal, serhiy.storchaka
priority: normal
severity: normal
status: open
title: Default values for AST Nodes
type: enhancement
versions: Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue39981>
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