There are two kinds of format strings in Python: those acceptable to
the Python built-in format operator
%, labelled as
‘python-format’, and those acceptable to the
of the ‘str’ object.
% format strings are described in
Python Library reference /
2. Built-in Types, Exceptions and Functions /
2.2. Built-in Types /
2.2.6. Sequence Types /
22.214.171.124. String Formatting Operations.
Python brace format strings are described in PEP 3101 – Advanced String Formatting, http://www.python.org/dev/peps/pep-3101/.