Python: Logging TypeError: not all arguments converted during string formatting

Question

Here is what I am doing

>>> import logging
>>> logging.getLogger().setLevel(logging.INFO)
>>> from datetime import date
>>&g         


        

Answer 1

You cannot use new-style formatting when using the logging module; use %s instead of {}.

logging.info('date=%s', date)

The logging module uses the old-style % operator to format the log string. See the debug method for more detail.

If you really want to use str.format() string formatting, consider using custom objects that apply the formatting 'late', when actually converted to a string:

class BraceMessage(object):
    def __init__(self, fmt, *args, **kwargs):
        self.fmt = fmt
        self.args = args
        self.kwargs = kwargs

    def __str__(self):
        return self.fmt.format(*self.args, **self.kwargs)

__ = BraceMessage

logging.info(__('date={}', date))

This is an approach the Python 3 logging module documentation proposes, and it happens to work on Python 2 too.