"MKoool" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Hi everyone,
>
> I am doing several operations on lists and I am wondering if python has
> anything built in to get every member of several objects that are in an
> array,
<-snip->
>
Here's some sample code to show you how list comprehensions and generator
expressions do what you want.
-- Paul
class A(object):
def __init__(self,val):
self.a = val
# define _repr_ to make it easy to print list of A's
def __repr__(self):
return "A(%s)" % str(self.a)
Alist = [ A(i*1.5) for i in range(5) ]
print Alist
# create new list of .a attributes, print, and sum
Alist_avals = [ x.a for x in Alist ]
print Alist_avals
print sum(Alist_avals)
# if original list is much longer...
Alist = [ A(i*1.5) for i in range(500000) ]
# ... creating list comprehension will take a while...
print sum( [ x.a for x in Alist ] )
# ... instead use generator expression - avoids creation of new list
print sum( x.a for x in Alist )
--
http://mail.python.org/mailman/listinfo/python-list
