[issue29546] A more helpful ImportError message

[Donald Stufft]

Changes by Donald Stufft :


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[issue29546] A more helpful ImportError message

[Barry A. Warsaw]

Barry A. Warsaw added the comment:


New changeset 1bc156430bad8177b5beecf57979628c1d071230 by Barry Warsaw 
(Matthias Bussonnier) in branch 'master':
bpo-29546: Improve from-import error message with location (#103)
https://github.com/python/cpython/commit/1bc156430bad8177b5beecf57979628c1d071230


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[issue29546] A more helpful ImportError message

[Serhiy Storchaka]

Changes by Serhiy Storchaka :


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[issue29546] A more helpful ImportError message

[Larry Hastings]

Changes by Larry Hastings :


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[issue29546] A more helpful ImportError message

[Barry A. Warsaw]

Changes by Barry A. Warsaw :


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resolution:  -> fixed
stage:  -> resolved
status: open -> closed

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[issue29546] A more helpful ImportError message

[Ivan Levkivskyi]

Changes by Ivan Levkivskyi :


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[issue29546] A more helpful ImportError message

[Matthias Bussonnier]

Matthias Bussonnier added the comment:

See https://github.com/python/cpython/pull/103 that implements Barry's proposed 
format.

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[issue29546] A more helpful ImportError message

[Matthias Bussonnier]

Changes by Matthias Bussonnier :


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[issue29546] A more helpful ImportError message

[Matthias Bussonnier]

Matthias Bussonnier added the comment:

I'm unsure I understand changing only the default __str__() method. You will 
anyway have to format the message differently depending on whether you raise 
from a from-import or a from-import-* or any other locations. 

AFAIU you "just" need the following 

  -PyErr_SetImportError(PyUnicode_FromFormat("cannot import name %R", 
name), pkgname, pkgpath);
  +PyErr_SetImportError(
  +PyUnicode_FromFormat("cannot import name %R from %R (%S)",
  +name, pkgname, pkgpath),
  +pkgname, pkgpath);

To use Barry format (though keeping quotes around identifiers to match current 
behavior).
(And similar if path is null). 

I'm unsure if you meant to provide a set of "format-template" to ImportError 
that are guarantied to be called with format(name=..., path=...) but I doubt it.

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[issue29546] A more helpful ImportError message

[Brett Cannon]

Brett Cannon added the comment:

Thanks to Matthias' PR the information is all there in the exception, but the 
message has not been changed. One idea for this -- depending on how much C code 
you want to write -- is to provide a default message for __str__() that changes 
depending on whether 'path' and/or 'name' are set. Then you can just set the 
attributes in the __init__() and have __str__() take care of providing a common 
message format. Another option is to do all of that in the __init__() so that 
BaseException.args continues to have the full error message (but that is added 
overhead if the __str__() is never taken of the exception). I also have no clue 
how much C code this would take :) (This is all why I have toyed with the idea 
of re-implementing the exceptions in Python for easier customization.)

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[issue29546] A more helpful ImportError message

[Brett Cannon]

Brett Cannon added the comment:


New changeset bc4bed440504597cac47d0a215ee094bfa99ba7e by Brett Cannon in 
branch 'master':
bpo-29546: Set 'path' on ImportError for ``from ... import ...`` (GH-91)
https://github.com/python/cpython/commit/bc4bed440504597cac47d0a215ee094bfa99ba7e


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[issue29546] A more helpful ImportError message

[Matthias Bussonnier]

Changes by Matthias Bussonnier :


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[issue29546] A more helpful ImportError message

[Matthias Bussonnier]

Changes by Matthias Bussonnier :


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pull_requests: +62, 63, 64

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[issue29546] A more helpful ImportError message

[Matthias Bussonnier]

Changes by Matthias Bussonnier :


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pull_requests: +62, 63

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[issue29546] A more helpful ImportError message

[Matthias Bussonnier]

Matthias Bussonnier added the comment:

Unsure if GitHub PR autolinks here. 

I'm attempting part of that at https://github.com/python/cpython/pull/91

AFAICT with my little knowledge of CPython internal, `name` and `path` where 
unset for `from ... import`. 

I'll be happy to change the formatting as well but I suspect this will lead to 
lot of bikeshedding.

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nosy: +mbussonn

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[issue29546] A more helpful ImportError message

[Brett Cannon]

Changes by Brett Cannon :


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type:  -> enhancement

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[issue29546] A more helpful ImportError message

[Brett Cannon]

Brett Cannon added the comment:

So 'path' already exists on ImportError so tweaking the message when the path 
is known wouldn't be difficult 
(https://docs.python.org/3/library/exceptions.html?highlight=importerror#ImportError).

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nosy: +brett.cannon

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[issue29546] A more helpful ImportError message

[Barry A. Warsaw]

New submission from Barry A. Warsaw:

I haven't really thought about this deeply but I've observed that there are 
lots of cases where a user will report getting an ImportError trying to import 
a name from a module, where it turns out that the problem is that the module is 
coming from an unexpected location.  Examples include pip installed packages 
overriding system packages, or unexpected vendorized wheels.

The standard first response is typically, "can you please run this to tell us 
where the foo library is coming from?"  E.g.

```
^^ this is indicative of an old version of urllib3. Can you please double 
check whether you have an old urllib3 installed e.g. in /usr/local or ~/.

Testing:

$ python3 -c 'import urllib3; print(urllib3.__file__)'

should return:

/usr/lib/python3/dist-packages/urllib3/__init__.py

and might tell you where else a locally installed urllib3 is to be found if it 
doesn't return that value.
```

It would be kind of useful if the original ImportError showed you where the 
module came from (i.e. its __file__), if such information can be discerned.  
E.g.:

```
>>> import requests; requests.__version__.split('.')  
Traceback (most recent call last):
   File "", line 1, in 
   File "/usr/lib/python2.7/dist-packages/requests/__init__.py", line 
61, in 
 from .packages.urllib3.exceptions import DependencyWarning
ImportError: cannot import name DependencyWarning from 
requests.packages.urllib3.exceptions 
(/usr/local/lib/python3.5/site-packages/requests/packages/urllib3.py)
```

If you saw that in a bug report, you'd almost immediately know that the user 
has some local override that's potentially causing the problem.

--
components: Interpreter Core
messages: 287708
nosy: barry
priority: normal
severity: normal
status: open
title: A more helpful ImportError message
versions: Python 3.7

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