On 09/12/13 04:46, Varuna Seneviratna wrote:
do not understand what is meant by "A /namespace/ is a mapping from
names to objects". How I understand to be a namespace is a particular
space within which a particular name is unique.
That's correct.
But a name on its own can refer to anything.
But it can't refer to nothing, in Python every name must refer to some
kind of object for it to exist (even if the object is None).
So for python to know what a given name refers to it must have a mapping
between name and object(data, function, class etc)
space set of built-in names the name "abs()" is used to denote the
function which returns the absolute value of a number and no other
function(operation) can be named abs() as a built-in function.
That's not true. Names and objects (including functions) are only
loosely bound together. I can easily create another name for the
abs function:
>>> oldabs = abs
>>> oldabs(5) == abs(5)
True
I can even name a completely different function 'abs'
>>> def abs(n): return n
Now abs is a completely different function, but oldabs is still
referring to the original built-in function.
Every name refers to exactly one object, but what object it refers to is
not necessarily what it started out as. And there may be several names
for the same object. So you need to maintain a mapping. And that mapping
defines what the namespace contains.
HTH
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.flickr.com/photos/alangauldphotos
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