Terry J. Reedy <tjre...@udel.edu> added the comment:
The parser is not involved here. The transformed code is *not* equivalent to
"1=2; print(1)" because you replace 'a' with the string '1', not the int 1.
The result is to transform
"globals()['a']=2; print(globals()['a'])" to
"globals()['1']=2; print(globals()['1'])"
This works because globals() is a regular dict.
If one does try to make the code equivalent to "1=2; print(1)" by replacing
with 1, the result is an error.
Traceback (most recent call last):
File "F:\Python\a\tem4.py", line 19, in <module>
print(ast.unparse(newast))
File "C:\Programs\Python310\lib\ast.py", line 1567, in unparse
return unparser.visit(ast_obj)
File "C:\Programs\Python310\lib\ast.py", line 805, in visit
return "".join(self._source)
TypeError: sequence item 1: expected str instance, int found
With unparse removed, I get a compile error when the identifier type is checked.
Traceback (most recent call last):
File "F:\Python\a\tem4.py", line 19, in <module>
c = compile(newast,'','exec')
TypeError: AST identifier must be of type str
In the binary example, unparsing gives an infinite recursion error with this
repeated sequence.
File "C:\Programs\Python310\lib\ast.py", line 1372, in visit_BinOp
self.traverse(node.left)
File "C:\Programs\Python310\lib\ast.py", line 798, in traverse
super().visit(node)
File "C:\Programs\Python310\lib\ast.py", line 410, in visit
return visitor(node)
Without unparse, the compile call crashes. (In IDLE, this means there is an
unrequested restart of the Shell subprocess that executes user code, without
IDLE crashing.) I suspect that there is a related loop in the compile C code
that crashes the process before any checking is done. If so, the situation
would be similar to your #42887 and we may not be able to do anything.
----------
nosy: +terry.reedy
title: Incorrect behavior of Python parser after ast node of test program
being modified -> Incorrect behavior after ast node visits
versions: -Python 3.6, Python 3.7
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<https://bugs.python.org/issue42889>
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