[issue19257] Sub-optimal error message when importing a non-package

[Brett Cannon]

Brett Cannon  added the comment:

I'm going to make a call and say the chained exception should stay. If people 
want to start the discussion again they can.

--
resolution:  -> rejected
stage: patch review -> resolved
status: open -> closed

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[issue19257] Sub-optimal error message when importing a non-package

[Éric Araujo]

Éric Araujo added the comment:

That makes a lot of sense.  I guess this is Brett’s call.

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[issue19257] Sub-optimal error message when importing a non-package

[Antoine Pitrou]

Antoine Pitrou added the comment:

 If you only had the latter exception all you would know is Python
 doesn't consider datetime a package but you wouldn't know why that is 
 unless you knew the exact definition (the __path__ attribute exists). 
 Having the former exception helps make that a bit more obvious if you 
 didn't already know it.

I don't think someone who doesn't know about __path__ would be very enlightened 
by the error message. Also, I don't think error messages have a role in 
teaching about the implementation details of features, so I'd vote for removing 
the __context__ here.

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nosy: +pitrou

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[issue19257] Sub-optimal error message when importing a non-package

[R. David Murray]

R. David Murray added the comment:

Antoine: down that path lies Microsoft's An error has occurred error 
messages.  The point of the extra information is not to inform the end user, it 
is to make it possible for an expert to solve the problem, and for it to be 
findable in a web search.

Now, whether or not there are enough different things that the second error 
could be chained off of to make that worthwhile in this case is something Brett 
or Eric will have to answer.  My guess is that there *potentially* are, even 
though this one is the most common, but that's just a guess since I haven't 
studied importlib.

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[issue19257] Sub-optimal error message when importing a non-package

[Antoine Pitrou]

Antoine Pitrou added the comment:

 Antoine: down that path lies Microsoft's An error has occurred error
 messages.  The point of the extra information is not to inform the end
 user, it is to make it possible for an expert to solve the problem,
 and for it to be findable in a web search.

I don't know how that's related. Here the error is trying to import from
a package while the module isn't a package. The solution is either to
change the import to something else, or to turn the non-package into a
package. None of these involve doing anything explicitly with __path__,
so the original error is a distraction.

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[issue19257] Sub-optimal error message when importing a non-package

[Éric Araujo]

Éric Araujo added the comment:

Fix is simple:

--- a/Lib/importlib/_bootstrap.py
+++ b/Lib/importlib/_bootstrap.py
@@ -1519,7 +1519,7 @@ def _find_and_load_unlocked(name, import
 path = parent_module.__path__
 except AttributeError:
 msg = (_ERR_MSG + '; {} is not a package').format(name, parent)
-raise ImportError(msg, name=name)
+raise ImportError(msg, name=name) from None

Manual testing confirms the fix.  Is a unit test needed?  Should this wait for 
3.5?

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nosy: +eric.araujo

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[issue19257] Sub-optimal error message when importing a non-package

[Éric Araujo]

Changes by Éric Araujo mer...@netwok.org:


--
keywords: +needs review, patch
stage:  - patch review

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[issue19257] Sub-optimal error message when importing a non-package

[STINNER Victor]

STINNER Victor added the comment:

 --- a/Lib/importlib/_bootstrap.py
 +++ b/Lib/importlib/_bootstrap.py

Eric, please attach the patch as a file to the issue, so it can be easily 
reviewed on Rietveld.

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nosy: +haypo

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[issue19257] Sub-optimal error message when importing a non-package

[Éric Araujo]

Éric Araujo added the comment:

I figured it would take less time for someone to go to the file and make the 
edit than download and apply a patch file, but as you wish :)

--
Added file: http://bugs.python.org/file34392/fix-import-not-package-tb.diff

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[issue19257] Sub-optimal error message when importing a non-package

[STINNER Victor]

STINNER Victor added the comment:

I figured it would take less time for someone to go to the file and make the 
edit than download and apply a patch file, but as you wish :)

It's not to apply the patch, but to review it. The Rietveld tool helps to 
review a patch online, it displays more context (lines before/after) ;-)

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[issue19257] Sub-optimal error message when importing a non-package

[Brett Cannon]

Brett Cannon added the comment:

Is it confusing though? If you only had the latter exception all you would know 
is Python doesn't consider datetime a package but you wouldn't know why that is 
unless you knew the exact definition (the __path__ attribute exists). Having 
the former exception helps make that a bit more obvious if you didn't already 
know it.

--
versions: +Python 3.5 -Python 3.4

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[issue19257] Sub-optimal error message when importing a non-package

[Éric Araujo]

Éric Araujo added the comment:

 If you only had the latter exception all you would know is Python
 doesn't consider datetime a package but you wouldn't know why that is
Well, I’d be satisfied with that.  Looking at the doc or importing just 
datetime would let me know it’s a module, not a package.

 unless you knew the exact definition (the __path__ attribute exists).
To me that’s an implementation detail.  The real definition in my mental model 
is that modules are files and packages are directories.  __path__ is advanced 
stuff.

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[issue19257] Sub-optimal error message when importing a non-package

[R. David Murray]

R. David Murray added the comment:

That's only true if you are dealing with files and directories though.  The 
import system can deal with much more than that, in which case the absence 
__path__ could be an important bit of debugging information.

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nosy: +r.david.murray

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[issue19257] Sub-optimal error message when importing a non-package

[R. David Murray]

R. David Murray added the comment:

Actually, it could be important even if you are dealing with files and 
directories (or I'm confused and __path__ is always about same :), since you 
could be dealing with an alternate loader.

Our policy is not to hide the chained traceback unless *all* of the information 
in the chain has been expressed in the replacement traceback error message.

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[issue19257] Sub-optimal error message when importing a non-package

[Alex Gaynor]

New submission from Alex Gaynor:

Use case:

Alexanders-MacBook-Pro:pypy alex_gaynor$ python3.3
Python 3.3.2 (default, May 29 2013, 14:03:57)
[GCC 4.2.1 Compatible Apple LLVM 4.2 (clang-425.0.28)] on darwin
Type help, copyright, credits or license for more information.
 import datetime.datetime
Traceback (most recent call last):
  File frozen importlib._bootstrap, line 1521, in _find_and_load_unlocked
AttributeError: 'module' object has no attribute '__path__'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File stdin, line 1, in module
ImportError: No module named 'datetime.datetime'; datetime is not a package




Showing the user the original module has no attribute __path__ error is just 
confusing, we should hide it.

--
messages: 199847
nosy: alex
priority: normal
severity: normal
status: open
title: Sub-optimal error message when importing a non-package

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[issue19257] Sub-optimal error message when importing a non-package

[Berker Peksag]

Changes by Berker Peksag berker.pek...@gmail.com:


--
nosy: +brett.cannon, eric.snow
versions: +Python 3.4

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