How can I log a dictionary into a log file?

Question

I have a dictionary:

 d = {name : "John", age: 10}.  

And a log file setup as:

logging.basicConfig(level = logging.DEBUG, filename = "sample.log") 

Is it possible to log this dictionary into the "sample.log" file? If yes, how can I do it?

Answer 1

Simple solution that works

The logging functions will convert the '%s' to string representation (and if the object happens to be a container, then repr() will be used for the contained objects)

import logging logging.basicConfig(level=logging.DEBUG, filename='sample.log') logging.debug('Sample dict log: %s', {'name' : "John", 'age': 10}) 

How it shows in the log file:

DEBUG:root:Sample dict log: {'age': 10, 'name': 'John'} 

If you have custom objects (e.g. instances of your own classes), you should implement a sensible __str__ and/or __repr__ for it, and the above will work without any hacks.

More on this here Difference between __str__ and __repr__ in Python

JSON is not very good for this

For objects that aren't JSON-like (object instances, datetime, etc), json.dumps() would require a custom serializer e.g. with datetime objects you get:

TypeError: datetime.datetime(...) is not JSON serializable

This goes for any type that isn't supported by json.dumps()

Whereas the logging module would figure out a good representation for the object

Answer 2

Simple you can use

dict_data = {"test":"data"} logger.info("Loging dict ---> {0}".format(dict_data))