20.16. format(): Format a value

This function converts a value to a formatted representation. The general form is:

format(value[, spec])

For built-in types, the spec has the syntax as that described in Section 9.4, “The string .format() method” between “:” and the closing “}”.
```
>>> x = 34.56
>>> format(x, '9.4f')
'  34.5600'
>>> '{0:9.4f}'.format(x)
'  34.5600'
```
You can define how this function works for a user-defined class by defining the special method described in Section 26.3.13, “__format__: Implement the format() function”.
If the spec argument is omitted, the result is the same as str(value).

Python 2.7 quick reference