ast.parse(..., mode='single') parses of multiple statements which are then not unparsed

[tom-pytel]

Bug report

Bug description:

$ ./python
Python 3.14.0a4+ (heads/test:d906bde250, Feb  2 2025, 11:08:38) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import ast
>>> a = ast.parse('i = 1; j = 2', mode='single')
>>> print(ast.dump(a, indent=2))
Interactive(
  body=[
    Assign(
      targets=[
        Name(id='i', ctx=Store())],
      value=Constant(value=1)),
    Assign(
      targets=[
        Name(id='j', ctx=Store())],
      value=Constant(value=2))])
>>> ast.unparse(a)
'j = 2'

My guess the ast.parse() should probably error?

CPython versions tested on:

3.14, 3.12, 3.13, 3.11, 3.10

Operating systems tested on:

Linux

Linked PRs

• gh-129598: allow multi stmts for ast single with ';' #129620

[tomasr8]

mode='single' is for Interactive input which always returns ast.Interactive. i = 1; j = 2 is a valid interactive_input.

It looks like we are missing a specialized visit_Interactive in the _Unparser visitor:

cpython/Lib/ast.py

Lines 666 to 669 in 808071b

	class _Unparser(NodeVisitor):
	"""Methods in this class recursively traverse an AST and
	output source code for the abstract syntax; original formatting
	is disregarded."""

Would you like to fix this? Otherwise I can send a fix later

[tom-pytel]

Sure, will send something up later.