Syntax help

[Steven D'Aprano]

On Wed, 26 Jan 2011 00:08:41 -0800, sl33k_ wrote:

> How to read syntax like this given in the documentation of python?
> (Newbie)
> 
> defparameter   ::=  parameter ["=" expression]
> 
> http://docs.python.org/reference/compound_stmts.html#function-
definitions

See here for an explanation:

http://docs.python.org/reference/introduction.html#notation


What you are looking at is not Python code, instead it is a formal 
description of what Python syntax looks like, based on a slightly 
modified BNF syntax:

http://en.wikipedia.org/wiki/Backus–Naur_Form

This tells you that a "defparameter" looks like a "parameter" followed 
optionally by an equals sign and an expression.

For example, here is a line of Python code:

    def function(x, y=42**3):

"x" is a defparameter made up of a parameter on it's own, while "y=42**3" 
is a defparameter made up of three parts: the parameter part "y", the 
equals sign, and the expression part "42**3".



-- 
Steven