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Re: [Numpy-discussion] numarraycore
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From: Colin J. W. <cj...@sy...> - 2004-05-05 23:00:54
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Todd Miller wrote:<br>
<blockquote type="cite"
cite="mid...@ha...">
<pre wrap="">On Wed, 2004-05-05 at 16:27, Colin J. Williams wrote:
</pre>
<blockquote type="cite">
<pre wrap="">It would help to have some documentation on the purpose and usage of the
class UsesOpPriority and its variable op_priority.
</pre>
</blockquote>
<pre wrap=""><!----></pre>
</blockquote>
Todd,<br>
<br>
Thanks for this, perhaps it could be added to the pdf . I like the
basic idea.<br>
<blockquote type="cite"
cite="mid...@ha...">
<pre wrap="">The basic idea was that NumArray subclasses which want to use numarray
operators would:
1. subclass from UsesOpPriority </pre>
</blockquote>
UsesOpPriority has no methods and thus, to access the methods of
NumArray, it would appear to be necessary to subclass from NumArray.<br>
<blockquote type="cite"
cite="mid...@ha...">
<pre wrap="">
2. set a class level op_priority > 0.
NumArrays have op_priority 0, higher priorities are given "precedence".
Thus, given A=NumArray(...) and B=NumArraySubclass(...), and
A.op_priority==0 and B.op_priority==1, then:
A+B would execute as B.__radd__(A) rather than A.__add__(B) and hence
the type(A+B) could be NumArraySubclass rather than NumArray. Different
subclasses could use higher or lower op_priorities to perform the same
kind of operator resolution among themselves.
</pre>
</blockquote>
I wonder about the desirability of having different levels of priority
for the same level of subclassing and am puzzled that a float variable
is used for the priority.<br>
<br>
It would nice if this depth could be determined automatically. Perhaps
something like the script below could be used.<br>
<br>
Colin W.<br>
<blockquote type="cite"
cite="mid...@ha...">
<pre wrap="">
Todd
</pre>
</blockquote>
# tClassing.py<br>
<br>
class A:<br>
def __init__(self):<br>
self.p= 0<br>
def prior(self):<br>
self.p+= 1<br>
class B(A):<br>
def __init__(self):<br>
A.__init__(self)<br>
self.prior()<br>
class C(B):<br>
def __init__(self):<br>
B.__init__(self)<br>
self.prior()<br>
<br>
print A().p<br>
print B().p<br>
c= C()<br>
print 'Priority for C methods:', c.p<br>
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