Modern Python Standard Library Cookbook

How it works...

The string.Formatter supports the same language that the str.format method supports. Practically, it parses expressions contained with {} according to what Python calls format string syntax. Everything outside of {} is preserved as is, while anything within {} is parsed for the field_name!conversion:format_spec specification. So, as our field_name doesn't contain ! or :, it can be anything else.

The field_name extracted is then provided to Formatter.get_field to look up the value of that field in the provided arguments of the format method.

So, for example, take an expression like:

string.Formatter().format("Hello {name}", name='Alessandro')

This leads to:

Hello Alessandro

Because the {name} is identified as a block to parse, ...