"filtered view" upon lists?

[Jorge Godoy]

Wildemar Wildenburger <wildemar at freakmail.de> writes:

> I don't know how else to call what I'm currently implementing: An object that
> behaves like a list but doesn't store it's own items but rather pulls them
> from a larger list (if they match a certain criterion).
> Changes to the filter are instantly reflected in the underlying list.
> Clear enough?

It looks like you're implementing a callable to me.  This is a method that
returns results based on some input -- here your original list and filter.

Then you'll use this method wherever you need that filtered list.

> Ok, so I figured that this is generic enough to be found in some standard
> module already (I've had this often enough: Painfully implementing s/th and
> then finding it in the libs some weeks later.).

I don't believe it is generic.  Nobody knows your data specs or filtering
needs. 

> Any pointers?

Use of list comprehension might make it easier to code this:


def myCallable(my_list, filter):
    filtered_list = [(item) for item in my_list if filter(item)]
    return filtered_list


Example of full code:

>>> test_list = range(10)
>>> filter = lambda x: not x%2
>>> def myCallable(list, filter):
...     filtered_list = [(item) for item in list if filter(item)]
...     return filtered_list
... 
>>> myCallable(test_list, filter)
[0, 2, 4, 6, 8]
>>> for item in myCallable(test_list, filter):
...     print "See?  I'm", item
... 
See?  I'm 0
See?  I'm 2
See?  I'm 4
See?  I'm 6
See?  I'm 8
>>> 


-- 
Jorge Godoy      <jgodoy at gmail.com>