UnicodeDecodeError when logging an Exception in Python

Question

I'm using Python 2.7.9. x32 on Win7 x64.

When I'm logging an Exception containing Umlauts, I always receive
UnicodeDecodeError: 'ascii' codec can't decode byte 0xfc in position 39: ordinal not in range(128)

My example code is:

except Exception as e:
            logging.error('Error loading SCMTool for repository '
                          '%s (ID %d): %s' % (repo.name, repo.id, e),
                          exc_info=1)

The Exception being logged is WindowsError: [Error 267] Der Verzeichnisname ist ungültig. The Problem is based on the "ungÜltig" umlaut.

After removing the last %s and the e it works without a problem.

This happens everytime an exception is logged, therefore changing every logger is no alternative.

Does anyone have an idea how to make Exception return a unicode string globally?

Martijn Pieters · Accepted Answer · 2015-02-20 10:42:58Z

15

You are trying to interpolate a unicode object into a str template, triggering an implicit encoding.

Use a unicode template; logging can handle Unicode just fine:

logging.error(u'Error loading SCMTool for repository '
              '%s (ID %d): %s' % (repo.name, repo.id, e),
              exc_info=1)

Two additional tips:

You don't have to do the interpolation yourself; if you pass in the 3 elements to interpolate as separate arguments, logging will interpolate for you, but only if the message is actually going to be emitted.
If you use logging.exception() the message is logged at the ERROR level and exc_info is set for you; it gets you the same result but is more easily recognised when reading your code later. Either way, the exception is already included in that case, no need to include it again in the message.

As such, I'd use:

logging.exception(
    'Error loading SCMTool for repository %s (ID %d)',
    repo.name, repo.id)

answered Feb 20, 2015 at 10:42

Martijn Pieters

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11 Comments

Seega Over a year ago

This is not really my code, I'm using Reviewboard which contains a lot files with multiple Exception loggings. Is there no more central way? Where I do not have to touch all files.

Martijn Pieters Over a year ago

Perhaps you should file a bug with the Reviewboard project then?

Martijn Pieters Over a year ago

There is no more 'central' way, this is a bug with how exceptions are being handled.

Seega Over a year ago

I found the root cause. On one maschine I'M using Win7 english (here it works) And on the other german (Doesn't work). With your fix, the Exception WindowsError: [Error 267] Der Verzeichnisname ist ungültig' is logged. This contains an Ü which cannot be encoded to ascii. Thanks for your help!

Martijn Pieters Over a year ago

@Seega: ah, I see what you mean, I misunderstood. Glad it is now working! :-D

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