You can access Python’s built-in help using the help() function with the name of any function inside the parentheses:

Help on built-in function round in module __builtin__:

    round(number[, ndigits]) -> floating point number
    Round a number to a given precision in decimal digits (default 0 digits).
    This always returns a floating point number.  Precision may be negative.

This provides a basic description of what the function does as well as its required and optional arguments. Anything inside the () but not inside the [] is a required argument that needs to be provided in the appropriate order. So, this help document tells us that number is required for round to work and we could call round as

>>> round(10.9)

Anything inside the [] is an optional argument, so we don’t have to include it. If we want to include it, in this case to specify the number of digits to round to, we can either include all of the optional arguments in order, or we can give the name of the optional argument we want to specify followed by an equals sign and the value we want to use.

>>> round(11.21, 1)

>>> round(11.21, ndigits=2)

Providing the name of the optional argument can make it easier to remember what the function is doing and can also be useful if there are several optional arguments and we want to use the default values for some of them.