[ Python 常見問題 ] How to change the format of logged messages temporarily, in Python?

Source From Here 
Question 
What is the simplest method for temporarily changing the logging message format, in Python (through the logging module)? 

How-To 
Here is a simple solution, that can be deduced from Vinay Sajip's own HOWTO; it basically updates the logging formatter with setFormatter(): 

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1. import logging  
2.   
3. logger = logging.getLogger()  # Logger  
4. logger_handler = logging.StreamHandler()  # Handler for the logger  
5. logger.addHandler(logger_handler)  
6.   
7. # First, generic formatter:  
8. logger_handler.setFormatter(logging.Formatter('%(message)s'))  
9. logger.error('error message')  # Test  
10.   
11. # New formatter for the handler:  
12. logger_handler.setFormatter(logging.Formatter('PROCESSING FILE xxx - %(message)s'))  
13. logger.error('error message')  # Test  

This correctly produces: 

error message 
PROCESSING FILE xxx - error message

Supplement 
* FAQ - How to get the list all existing loggers using python.logging module 

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1. import logging  
2. loggers = [logging.getLogger(name) for name in logging.root.manager.loggerDict]