Re: at what complexity, a comparison fails ?
Robert Kern wrote: Stef Mientki wrote: hello, I had a program that worked perfectly well. In this program modules were dynamically added, just by putting the file in a predefined directory. Now one of the interface mechanisms was to see if some parameter was changed in a an instance, by comparing the value from the instance with its previous value This went all well, untill I added a too complex variable, then the program stopped working, without generating exceptions. So it seems that comparing a too complex value isn't allowed. the variable was something like: A = [ ndarray, ndarray, ..., [color,color,...], [float, float, ... ] ] So what I need was something like: if A != A_prev : ... do something A_prev = A And this crashes, or at least it doesn't work but also doesn't generate exceptions. It does seems to work, if A only contains 1 array. Why am I not allowed to compare A and A_prev ?? And in general, how complex might a list be to make a valid comparison, or what are the rules ? Remember that numpy arrays use rich comparisons. (ndarray1 != ndarray2) gives another array, not a boolean value. The resulting array cannot be used in an if clause. thanks guys, I'm glad that Python behaves as expected and can compare complex structures ;-) Robert you hit the nail right on its head, indeed I should be quit carefully with numpy arrays. cheers, Stef Mientki -- http://mail.python.org/mailman/listinfo/python-list
at what complexity, a comparison fails ?
hello, I had a program that worked perfectly well. In this program modules were dynamically added, just by putting the file in a predefined directory. Now one of the interface mechanisms was to see if some parameter was changed in a an instance, by comparing the value from the instance with its previous value This went all well, untill I added a too complex variable, then the program stopped working, without generating exceptions. So it seems that comparing a too complex value isn't allowed. the variable was something like: A = [ ndarray, ndarray, ..., [color,color,...], [float, float, ... ] ] So what I need was something like: if A != A_prev : ... do something A_prev = A And this crashes, or at least it doesn't work but also doesn't generate exceptions. It does seems to work, if A only contains 1 array. Why am I not allowed to compare A and A_prev ?? And in general, how complex might a list be to make a valid comparison, or what are the rules ? thanks, Stef Mientki -- http://mail.python.org/mailman/listinfo/python-list
Re: at what complexity, a comparison fails ?
On Mon, 31 Dec 2007 11:45:55 +0100, Stef Mientki wrote: Now one of the interface mechanisms was to see if some parameter was changed in a an instance, by comparing the value from the instance with its previous value This went all well, untill I added a too complex variable, then the program stopped working, without generating exceptions. So it seems that comparing a too complex value isn't allowed. Then you get the wrong impression. the variable was something like: A = [ ndarray, ndarray, ..., [color,color,...], [float, float, ... ] ] So what I need was something like: if A != A_prev : ... do something A_prev = A And this crashes, or at least it doesn't work but also doesn't generate exceptions. It does seems to work, if A only contains 1 array. Why am I not allowed to compare A and A_prev ?? You are allowed and you do in the above code. And in general, how complex might a list be to make a valid comparison, or what are the rules ? There are no rules about the complexity. Lists are compared element wise. If the lists are of the same length and all elements at the corresponding indexes compare equal, the lists are considered equal. Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: at what complexity, a comparison fails ?
On Mon, 31 Dec 2007 11:45:55 +0100, Stef Mientki wrote: hello, I had a program that worked perfectly well. In this program modules were dynamically added, just by putting the file in a predefined directory. Now one of the interface mechanisms was to see if some parameter was changed in a an instance, by comparing the value from the instance with its previous value This went all well, untill I added a too complex variable, then the program stopped working, without generating exceptions. What do you mean stopped working? So it seems that comparing a too complex value isn't allowed. the variable was something like: A = [ ndarray, ndarray, ..., [color,color,...], [float, float, ... ] ] Doesn't seem complex to me, and I daresay probably not to Python either -- although a lot depends on what ndarray and colour are. So what I need was something like: if A != A_prev : ... do something A_prev = A And this crashes, or at least it doesn't work but also doesn't generate exceptions. It crashes? Explain please. It does seems to work, if A only contains 1 array. Why am I not allowed to compare A and A_prev ?? And in general, how complex might a list be to make a valid comparison, or what are the rules ? As complicated as you like. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: at what complexity, a comparison fails ?
On Dec 31, 2:45 am, Stef Mientki [EMAIL PROTECTED] wrote: So what I need was something like: if A != A_prev : ... do something A_prev = A If A_prev is not declared prior to the if statement, you will get an error when you try to compare the non-existing variable to A. This code will work, at least for the snippet you provided. A_prev= if A != A_prev : ... do something A_prev = A Please cut and paste the exact error message in the future. -- http://mail.python.org/mailman/listinfo/python-list
Re: at what complexity, a comparison fails ?
Stef Mientki wrote: hello, I had a program that worked perfectly well. In this program modules were dynamically added, just by putting the file in a predefined directory. Now one of the interface mechanisms was to see if some parameter was changed in a an instance, by comparing the value from the instance with its previous value This went all well, untill I added a too complex variable, then the program stopped working, without generating exceptions. So it seems that comparing a too complex value isn't allowed. the variable was something like: A = [ ndarray, ndarray, ..., [color,color,...], [float, float, ... ] ] So what I need was something like: if A != A_prev : ... do something A_prev = A And this crashes, or at least it doesn't work but also doesn't generate exceptions. It does seems to work, if A only contains 1 array. Why am I not allowed to compare A and A_prev ?? And in general, how complex might a list be to make a valid comparison, or what are the rules ? I suspect that some of the objects in A have either undefined (or ill-defined) comparison methods, so that the overall list comparison does not do what you expect. I'm not sure what ndarray and color are, but check their comparison methods (you know, __cmp__, __lt__, __eq__, etc). (If that isn't clear, please see http://effbot.org/pyref/__lt__.htm.) --Hans -- http://mail.python.org/mailman/listinfo/python-list
Re: at what complexity, a comparison fails ?
Stef Mientki wrote: hello, I had a program that worked perfectly well. In this program modules were dynamically added, just by putting the file in a predefined directory. Now one of the interface mechanisms was to see if some parameter was changed in a an instance, by comparing the value from the instance with its previous value This went all well, untill I added a too complex variable, then the program stopped working, without generating exceptions. So it seems that comparing a too complex value isn't allowed. the variable was something like: A = [ ndarray, ndarray, ..., [color,color,...], [float, float, ... ] ] So what I need was something like: if A != A_prev : ... do something A_prev = A And this crashes, or at least it doesn't work but also doesn't generate exceptions. It does seems to work, if A only contains 1 array. Why am I not allowed to compare A and A_prev ?? And in general, how complex might a list be to make a valid comparison, or what are the rules ? Remember that numpy arrays use rich comparisons. (ndarray1 != ndarray2) gives another array, not a boolean value. The resulting array cannot be used in an if clause. -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
