Python 3 Object-Oriented Programming - Third Edition

Custom formatters

While these standard formatters apply to most built-in objects, it is also possible for other objects to define nonstandard specifiers. For example, if we pass a datetime object into format, we can use the specifiers used in the datetime.strftime function, as follows:

import datetime 
print("{the_date:%Y-%m-%d %I:%M%p }".format( 
    datetime.datetime.now())) 

It is even possible to write custom formatters for objects we create ourselves, but that is beyond the scope of this book. Look into overriding the __format__ special method if you need to do this in your code.

The Python formatting syntax is quite flexible but it is a difficult mini-language to remember. I use it every day and still occasionally have to look up forgotten ...