I don't understand generator.send()
#! /usr/bin/env python def ints(): i=0 while True: yield i i += 1 gen = ints() while True: i = gen.next() print i if i==5: r = gen.send(2) print "return:",r if i>10: break I thought the send call would push the value "2" at the front of the queue. Instead it coughs up the 2, which seems senseless to me. 1/ How should I view the send call? I'm reading the manual and dont' get it 2/ Is there a way to push something in the generator object? So that it becomes the next yield expression? In my code I was hoping to get 0,1,2,3,4,5,2,6,7 as yield expressions. Victor. -- Victor Eijkhout -- eijkhout at tacc utexas edu -- http://mail.python.org/mailman/listinfo/python-list
Re: I don't understand generator.send()
Chris Angelico wrote: > For what you're doing, there's a little complexity. If I understand, > you want send() to be like an ungetc call... you could do that like > this: > > > def ints(): >i=0 >while True: >sent=(yield i) >if sent is not None: > yield None # This becomes the return value from gen.send() > yield sent # This is the next value yielded >i += 1 I think this will serve my purposes. Thanks everyone for broadening my understanding of generators. Victor. -- Victor Eijkhout -- eijkhout at tacc utexas edu -- http://mail.python.org/mailman/listinfo/python-list
Re: English Idiom in Unix: Directory Recursively
Harrison Hill wrote: > No need - I have the Dictionary definition of recursion here: > > Recursion: (N). See recursion. If you tell a joke, you have to tell it right. Recursion: (N). See recursion. See also tail recursion. Victor. -- Victor Eijkhout -- eijkhout at tacc utexas edu -- http://mail.python.org/mailman/listinfo/python-list
scipy sparse matrix question
I can't find any detailed information about scipy.sparse. My specific question: what does "for x in A" give me when A is a sparse matrix? It seems to yield all nonzero locations, but in what kind of form? Very specifically: how do I get the (i,j) coordinates and the value from x? Victor. -- Victor Eijkhout -- eijkhout at tacc utexas edu -- http://mail.python.org/mailman/listinfo/python-list
Re: scipy sparse matrix question
Terry Reedy wrote: > > My specific question: what does "for x in A" give me when A is a sparse > > matrix? > > Try it and see what you get. Ah, how do I see what I get? If I print it it looks plausible, but I don't know how to pull it apart. It doesn't seem to be an array. Victor. -- Victor Eijkhout -- eijkhout at tacc utexas edu -- http://mail.python.org/mailman/listinfo/python-list
sort array, apply rearrangement to second
I have two arrays, made with numpy. The first one has values that I want to use as sorting keys; the second one needs to be sorted by those keys. Obviously I could turn them into a dictionary of pairs and sort by the first member, but I think that's not very efficient, at least in space, and this needs to be done as efficiently as possible. I could use a hand. Victor. -- Victor Eijkhout -- eijkhout at tacc utexas edu -- http://mail.python.org/mailman/listinfo/python-list
Re: sort array, apply rearrangement to second
Robert Kern wrote: > second[first.argsort()] Really cool. Thanks. > Ask numpy questions on the numpy mailing list. I will. I thought that this question would have an answer in a generic python idiom. Victor. -- Victor Eijkhout -- eijkhout at tacc utexas edu -- http://mail.python.org/mailman/listinfo/python-list
Re: MATLAB to Python?
MATLABdude wrote: > Also the > values themselves are not identical compared to the values of the > MATLAB program. In numerical analysis there is no such thing as identical. If they differ by 1.e-10 I'd call it close enough. The difference comes from differing numerical methods. Victor. -- Victor Eijkhout -- eijkhout at tacc utexas edu -- http://mail.python.org/mailman/listinfo/python-list
Generator question
So I have a generator, either as a free function or in a class and I want to generate objects that are initialized from the generated things. def generator(): for whatever: yield something class Object(): def __init__(self): self.data = # the next thing from generator I have not been able to implement this elegantly. For external reasons the following syntax is unacceptable: for g in generator(): ob = Object(g) I really want to be able to write "Object()" in any location and get a properly initialized object. Hints appreciated. Victor. -- Victor Eijkhout -- eijkhout at tacc utexas edu -- http://mail.python.org/mailman/listinfo/python-list
Re: Generator question
Dan Stromberg wrote: > You likely want a class variable: Sounds like an elegant solution. Thanks! Victor. -- Victor Eijkhout -- eijkhout at tacc utexas edu -- http://mail.python.org/mailman/listinfo/python-list
long int computations
I have two long ints, both too long to convert to float, but their ratio is something reasonable. How can I compute that? The obvious "(1.*x)/y" does not work. Victor. -- Victor Eijkhout -- eijkhout at tacc utexas edu -- http://mail.python.org/mailman/listinfo/python-list
Re: long int computations
Jerry Hill wrote: > >>> from __future__ import division > >>> long1/long2 > 0.5 Beautiful. Thanks so much guys. Victor. -- Victor Eijkhout -- eijkhout at tacc utexas edu -- http://mail.python.org/mailman/listinfo/python-list
Re: long int computations
Mensanator wrote: > You could try using the gmpy module. It supports arbitrary precision > floats, so converting long to float is no problem. I fear I may actually have to go symbolic. I'm now having to use the 12th root of 2, and I would like the twelfth power of that to be exactly 2. Victor. -- Victor Eijkhout -- eijkhout at tacc utexas edu -- http://mail.python.org/mailman/listinfo/python-list
Re: Python -- floating point arithmetic
Zooko O'Whielacronx wrote: > I'm starting to think that one should use Decimals by default and > reserve floats for special cases. Only if one has Power6 (or 7) which has hardware support for BCD. Otherwise you will have slow applications. Victor. -- Victor Eijkhout -- eijkhout at tacc utexas edu -- http://mail.python.org/mailman/listinfo/python-list
