On Tuesday 01 March 2005 02:50 pm, Anthony Liu wrote:
> Yes, that's helpful. Thanks a lot.
>
> But what if I wanna construct an array of arrays like
> we do in C++ or Java:
>
> myArray [][]
>
> Basically, I want to do the following in Python:
>
> myArray[0][1] = list1
> myArray[1][2] = list2
> myArray[2][3] = list3
>
> How to do this, gurus?
One answer is "don't". You might for example, use a
dictionary with 2-tuple keys:
dict = { (a,b): value1, (c,d):value2, ...}
this has some advantages over an array approach,
including the fact that you immediately can model
a sparsely-sampled domain (or one with non-integral
and/or unevenly spaced sampling points).
Filling such a dictionary evenly isn't hard:
data = {}
for i in range(20):
for j in range(10):
data[(i,j)] = your_func(i,j)
Accessing it might be a little dicey if you want to allow
for filling holes:
f = data.get( (i,j), 0)
(will return 0 if no value exists at (i,j)).
If you really do need a filled array of any size, though,
you probably don't want to use lists or dictionaries, but
actual *arrays* like those provided by the Numeric or
Numarray modules (these are scientific programming
extension modules for Python -- actually two implementations
of the same concept, with nearly identical usage, but
slightly different performance.
--
Terry Hancock ( hancock at anansispaceworks.com )
Anansi Spaceworks http://www.anansispaceworks.com
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