TypeError instead of SyntaxError for syntactically invalid gen exp #46491

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1. ntc2 commented on Mar 5, 2008

   

   ntc2mannequin

   on Mar 5, 2008

   MannequinAuthor

   More actions

   I have a file f1.py

   $ cat f1.py
   import os
   (lambda **x:x)(**dict(y,y for y in ()))

   and when I run it

   $ python f1.py
   Traceback (most recent call last):
     File "f1.py", line 1, in <module>
       import os
   TypeError: 'int' object is not iterable

   Notice that the TypeError exception is from the import os on line 1.
   But the import isn't the problem. The problem is the illegal
   generator expression on line 2. I.e. if

   $ cat f2.py
   #import os
   dict(y,y for y in ())

   then

   $ python f2.py
     File "f2.py", line 2
       dict(y,y for y in ())
   SyntaxError: Generator expression must be parenthesized if not sole argument

   The mess

   (lambda **x:x)(**dict(y,y for y in ()))

   is a simplified version of something I had about 100 lines into a
   file, but the resulting TypeError still complains about an import on
   line 1, which is really confusing.

   I'm using

   Python 2.5.2 (r252:60911, Mar 4 2008, 14:33:51)
   [GCC 3.4.4] on linux2

   for python.

   ################################################################################

   The above is probably a good enough description, but here's some more
   weirdness in case it's helpful:

   Some variations of f1.py cause the same error, but others don't.
   E.g. if f4.py is

   for c in [1]: pass
   (lambda **x:x)(**dict(y,y for y in ()))

   I get

   Traceback (most recent call last):
     File "f4.py", line 1, in <module>
       for c in [1]: pass
   TypeError: 'int' object is not iterable

   as before. But if f5.py is

   for c in "1": pass
   (lambda **x:x)(**dict(y,y for y in ()))

   running the script results in no output and a successful run

   $ echo $?
   0

   Finally, if f6.py is just the single line

   (lambda **x:x)(**dict(y,y for y in ()))

   then my 2.5.2 python has the same successful with no output result as
   for f5.py, but if I run f6.py in an older

   Python 2.5 (r25:51908, Oct 30 2006, 16:20:39)
   [GCC 3.4.4] on linux2

   python I get

   Exception exceptions.SyntaxError: ('Generator expression must be
   parenthesized if not sole argument', 1) in 'garbage collection' ignored
   Fatal Python error: unexpected exception during garbage collection
   zsh: abort (core dumped) python f6.py

   The older 2.5 python runs f5.py successfully with no output like 2.5.2 does.

   I searched the bug tracker for "TypeError: 'int' object is not
   iterable" and didn't find anything, so I'm assuming this bug is
   unknown. I'm sure someone will let me know if I'm mistaken =)

   I'd guess the problem has to do with a bad parse.
2. amauryfa commented on Mar 5, 2008

   

   amauryfa

   on Mar 5, 2008

   Contributor

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   Interestingly, in debug mode, the message "XXX undetected error" is
   printed to stderr.
   And this gives the solution: in ast.c, some calls did not check the
   return status.

   Committed revision 61240, will backport to 2.5.
   Thanks for the report!
   Thanks for the report!
3. jafo commented on Mar 20, 2008

   

   jafomannequin

   on Mar 20, 2008

   Mannequin

   More actions

   Back-ported to 2.5 and committed in rev 61675.
4. jafo

   closed this as completedon Mar 20, 2008
5. ezio-melotti

   transferred this issue fromon Apr 10, 2022