Is there a good way to trace what's going on under the hood wrt operator
overloading?
I am trying to understand what is happening in the code and output listed
below.
Why doesn't __getitem__ in mylist return the same result as the builtin
list object?
Does it have something to do with the start
On Fri, Jun 1, 2012 at 9:39 AM, Josh Benner sjben...@gmail.com wrote:
Is there a good way to trace what's going on under the hood wrt operator
overloading?
I am trying to understand what is happening in the code and output listed
below.
Why doesn't __getitem__ in mylist return the same
Changes by Terry J. Reedy tjre...@udel.edu:
--
resolution: - out of date
status: open - closed
___
Python tracker rep...@bugs.python.org
http://bugs.python.org/issue2102
___
Changes by Fred L. Drake, Jr. [EMAIL PROTECTED]:
--
assignee: fdrake -
___
Python tracker [EMAIL PROTECTED]
http://bugs.python.org/issue2102
___
___
Python-bugs-list
Changes by Sean Reifschneider [EMAIL PROTECTED]:
--
assignee: - fdrake
components: +Documentation -Interpreter Core
nosy: +fdrake
priority: - normal
__
Tracker [EMAIL PROTECTED]
http://bugs.python.org/issue2102
__
: Interpreter Core
files: t.py
messages: 62361
nosy: calvin
severity: normal
status: open
title: New style classes __ror__() operator overloading problem
type: behavior
versions: Python 2.4, Python 2.5
Added file: http://bugs.python.org/file9425/t.py
__
Tracker [EMAIL
Amaury Forgeot d'Arc added the comment:
Doc says:
http://docs.python.org/dev/reference/datamodel.html#object.__ror__
These functions are only called if the left operand does not support the
corresponding operation and the operands are of different types.
For operands of the same type, it is
compatibility. The documentation
should mention the different behaviour though.
--
title: New style classes __ror__() operator overloading problem - New style
vs. old style classes __ror__() operator overloading
__
Tracker [EMAIL PROTECTED]
http
On Jan 25, 8:52 pm, Hexamorph [EMAIL PROTECTED] wrote:
[EMAIL PROTECTED] wrote:
Hexamorph wrote:
You mean you want the ability to change for example the + operator
for ints to something like calculating the cosine instead of doing
addition?
Sure. Cosines are a monadic operation and
| Sure. Cosines are a monadic operation and the monadic '+' is a NOP,
so
| why shouldn't I define +45 to return cosine of 45, (presuming I
needed
| lots of cosines). I'd even let you define your own operators. Lots of
| programmers really liked '++' and '--', for examples.
One cannot
[EMAIL PROTECTED] wrote:
Diez B. Roggisch wrote:
No, there is no way. You would change general interpreter behavior if
you could set arbitrary operators for predefined types.
Start grumping...
Thank you, Diez.
If I ever design a language, please remind me that complete, easy,
[EMAIL PROTECTED] schrieb:
Diez B. Roggisch wrote:
No, there is no way. You would change general interpreter behavior if
you could set arbitrary operators for predefined types.
Start grumping...
Thank you, Diez.
If I ever design a language, please remind me that complete, easy,
[EMAIL PROTECTED] wrote:
Hexamorph wrote:
You mean you want the ability to change for example the + operator
for ints to something like calculating the cosine instead of doing
addition?
Sure. Cosines are a monadic operation and the monadic '+' is a NOP, so
why shouldn't I define +45 to
Diez B. Roggisch wrote:
No, there is no way. You would change general interpreter behavior if
you could set arbitrary operators for predefined types.
Start grumping...
Thank you, Diez.
If I ever design a language, please remind me that complete, easy,
well-documented access to the working
[EMAIL PROTECTED] schrieb:
If it were my choice, the plus sign would do this:
def itemadd( i1, i2 ):
if ( type(i1) == str ) or ( type(i2) == str ):
return str(i1) + str(i2)
else:
return i1 + i2
I'd like to redefine it so it works my way but operator overloading
If it were my choice, the plus sign would do this:
def itemadd( i1, i2 ):
if ( type(i1) == str ) or ( type(i2) == str ):
return str(i1) + str(i2)
else:
return i1 + i2
I'd like to redefine it so it works my way but operator overloading
seems strictly confined to classes I
Hexamorph wrote:
You mean you want the ability to change for example the + operator
for ints to something like calculating the cosine instead of doing
addition?
Sure. Cosines are a monadic operation and the monadic '+' is a NOP, so
why shouldn't I define +45 to return cosine of 45,
Hallo,
could you explaint me the difference between the two following
statements.
Python 2.5 (r25:51908, Oct 7 2006, 23:45:05)
[GCC 3.3.5 20050117 (prerelease) (SUSE Linux)] on linux2
Type help, copyright, credits or license for more information.
(1).__cmp__(10)
-1
1.__cmp__(10)
File stdin,
[EMAIL PROTECTED] wrote:
(1).__cmp__(10)
-1
Integer object (1) followed by method call .__cmp__(10)
1.__cmp__(10)
File stdin, line 1
1.__cmp__(10)
^
SyntaxError: invalid syntax
Floating point number 1. followed by __cmp__(10).
STeVe
--
On Thu, 08 Nov 2007 22:53:16 -0800, r.grimm wrote:
(1).__cmp__(10)
-1
As the dot is an operator like ``+`` or ``/`` you can also add spaces to
avoid the ambiguity:
In [493]: 1 . __cmp__(10)
Out[493]: -1
In [494]: 1 .__cmp__(10)
Out[494]: -1
Ciao,
Marc 'BlackJack' Rintsch
--
[EMAIL PROTECTED] wrote:
On Apr 4, 4:55 pm, Terry Reedy [EMAIL PROTECTED] wrote:
Ziga Seilnacht [EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
| This looks like a bug in Python. It works for all the other
| operators:
[SNIP]
| i ** 3
| 74088
|
| You should submit a bug
Hi,
for the fun I try operator overloading experiences and I didn't
exactly understand how it works.
Here is my try:
class myint(int):
def __pow__(self, value):
return self.__add__(value)
a = myint(3)
a ** 3
6
OK, it works. Now I try different way to achieve the same
looping wrote:
Hi,
for the fun I try operator overloading experiences and I didn't
exactly understand how it works.
Here is my try:
class myint(int):
def __pow__(self, value):
return self.__add__(value)
a = myint(3)
a ** 3
6
OK, it works. Now I try
On Apr 4, 3:36 am, looping [EMAIL PROTECTED] wrote:
Hi,
for the fun I try operator overloading experiences and I didn't
exactly understand how it works.
Here is my try: class myint(int):
def __pow__(self, value):
return self.__add__(value)
a = myint(3)
a ** 3
On Apr 4, 12:41 pm, 7stud [EMAIL PROTECTED] wrote:
On Apr 4, 3:36 am, looping [EMAIL PROTECTED] wrote:
Hi,
for the fun I try operator overloading experiences and I didn't
exactly understand how it works.
Here is my try: class myint(int):
def __pow__(self, value
On Apr 4, 12:41 pm, 7stud [EMAIL PROTECTED] wrote:
According to Python in a Nutshell(p.102), a name that is a slot can
only be bound(i.e. assigned to) inside the class body.
Upon closer reading, it actually says that the name __slots__ has to
be bound inside the class body for the slot
Ziga Seilnacht [EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
| This looks like a bug in Python. It works for all the other
| operators:
|
| class MyInt(int):
| ... __sub__ = int.__add__
| ... __mul__ = int.__add__
| ... __div__ = int.__add__
| ... __truediv__ =
On Apr 4, 4:55 pm, Terry Reedy [EMAIL PROTECTED] wrote:
Ziga Seilnacht [EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
| This looks like a bug in Python. It works for all the other
| operators:
[SNIP]
| i ** 3
| 74088
|
| You should submit a bug report to the bug tracker:
|
[EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
| FWIW:
| Python 2.5 (r25:51908, Jan 21 2007, 03:10:25)
| [GCC 3.4.6 20060404 (Red Hat 3.4.6-3)] on HOSTNAME_REDACTED
| Type help, copyright, credits or license for more information.
| class MyInt(int):
| ... __pow__ = int.__add__
|
looping wrote:
Hi,
for the fun I try operator overloading experiences and I didn't
exactly understand how it works.
Here is my try:
class myint(int):
def __pow__(self, value):
return self.__add__(value)
a = myint(3)
a ** 3
6
OK, it works. Now I try different
Fredrik Lundh [EMAIL PROTECTED] (FL) wrote:
FL Piet van Oostrum wrote:
The official Python documentation (language reference manual) talks a lot
about variables. So it seems silly to say that Python doesn't have
variables.
FL the language reference mostly uses the term variables when
Terry Reedy wrote:
Bruno Desthuilliers [EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
Terry Reedy wrote:
Bruno Desthuilliers [EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
The current namespace object, of course.
Implementing a namespace as a Python object (ie, dict)
Georg Brandl wrote:
Bruno Desthuilliers wrote:
Steven D'Aprano wrote:
On Sat, 07 Oct 2006 17:21:55 -0500, Tim Chase wrote:
With the caveat of the = mentioned in the subject-line (being
different from ==)...I haven't found any way to override
assignment in the general case.
Why would you
Terry Reedy wrote:
Bruno Desthuilliers [EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
The current namespace object, of course.
Implementing a namespace as a Python object (ie, dict) is completely
optional and implementation dependent. For CPython, the local namespace of
a
Bruno Desthuilliers [EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
Terry Reedy wrote:
Bruno Desthuilliers [EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
The current namespace object, of course.
Implementing a namespace as a Python object (ie, dict) is completely
Terry Reedy wrote:
Implementing a namespace as a Python object (ie, dict) is
completely optional and implementation dependent. For CPython, the
local namespace of a function is generally *not* done that way.
Sure, but this is all just theoretical talk anyway, right? I would
like to
On 9 Oct 2006 11:27:40 GMT, Antoon Pardon [EMAIL PROTECTED] wrote:
I honestly don't see why variable would be an inappropiate word to use.
AFAIU, python assignment seems to behave much like lisp and smalltalk
and I never heard that those communities found the word variable
inappropiate to
# [EMAIL PROTECTED] / 2006-10-08 11:44:18 +0100:
That's because assignment isn't an operator - that's why (for example)
print x = 33
would be a syntax error. This is a deliberate design decision about
which, history shows, there is little use complaining.
Just to clarify: not
Roman Neuhauser wrote:
People who complain often fail to see how
x = foo()
while x:
process(x)
x = foo()
is safer than
while x = foo():
process(x)
that's spelled:
for x in foo():
process(x)
in Python, or, if foo() just refuses be turned
Fredrik Lundh [EMAIL PROTECTED] writes:
or for the perhaps-overly-clever hackers,
for x in iter(lambda: foo() or None, None):
process(x)
for x in takewhile(foo() for _ in repeat(None)):
process (x)
--
http://mail.python.org/mailman/listinfo/python-list
Fredrik Lundh [EMAIL PROTECTED] writes:
or for the perhaps-overly-clever hackers,
for x in iter(lambda: foo() or None, None):
process(x)
for x in takewhile(bool, (foo() for _ in repeat(None))):
process(x)
Meh, both are ugly.
--
On 2006-10-10, Paul Rubin http wrote:
Fredrik Lundh [EMAIL PROTECTED] writes:
or for the perhaps-overly-clever hackers,
for x in iter(lambda: foo() or None, None):
process(x)
for x in takewhile(foo() for _ in repeat(None)):
process (x)
for x in takewhile(foo() for _ in
Antoon Pardon [EMAIL PROTECTED] writes:
for x in takewhile(foo() for _ in repeat(None)):
... print x
...
Traceback (most recent call last):
File stdin, line 1, in ?
TypeError: takewhile expected 2 arguments, got 1
Yeah, I cancelled and posted a followup
for x in takewhile(bool,
On 2006-10-10, Paul Rubin http wrote:
Fredrik Lundh [EMAIL PROTECTED] writes:
or for the perhaps-overly-clever hackers,
for x in iter(lambda: foo() or None, None):
process(x)
for x in takewhile(bool, (foo() for _ in repeat(None))):
process(x)
Meh, both are ugly.
Antoon Pardon [EMAIL PROTECTED] writes:
Suppose one has the following intention in mind:
while x = setup():
if y = pre_process() in ErrorCondition:
break
post_process(y)
else:
NormalTermination()
Maybe we need a new itertools function:
def forever(func, *args,
Steven D'Aprano [EMAIL PROTECTED] (SD) wrote:
SD Despite sloppy talk to the contrary (which I think most of us do from time
SD to time), Python doesn't have variables. It has names and objects. Names
SD are just labels -- there is no difference in behavior between the *names*
SD
Piet van Oostrum [EMAIL PROTECTED] writes:
The official Python documentation (language reference manual) talks a lot
about variables. So it seems silly to say that Python doesn't have
variables.
The symbols on the left side of = signs are called variables even in
Haskell, where they don't vary
Piet van Oostrum wrote:
The official Python documentation (language reference manual) talks a lot
about variables. So it seems silly to say that Python doesn't have
variables.
the language reference mostly uses the term variables when discussing
local variables and instance variables, and is
Paul Rubin wrote:
The symbols on the left side of = signs are called variables even in
Haskell, where they don't vary (you can't change the value of a
variable once you have set it).
at the language specification level, the things to the left side of =
signs are called targets in Python. if
Paul Rubin wrote:
The symbols on the left side of = signs are called variables even in
Haskell, where they don't vary (you can't change the value of a
variable once you have set it).
FWIW, that's the original, mathematical meaning of the word 'variable'.
They _do_ vary, but only when you call
On 2006-10-08, Steven D'Aprano [EMAIL PROTECTED] wrote:
On Sat, 07 Oct 2006 17:21:55 -0500, Tim Chase wrote:
With the caveat of the = mentioned in the subject-line (being
different from ==)...I haven't found any way to override
assignment in the general case.
Why would you want to do that?
Steven D'Aprano wrote:
On Sat, 07 Oct 2006 17:21:55 -0500, Tim Chase wrote:
With the caveat of the = mentioned in the subject-line (being
different from ==)...I haven't found any way to override
assignment in the general case.
Why would you want to do that?
For the same reason one would
Bruno Desthuilliers wrote:
Steven D'Aprano wrote:
On Sat, 07 Oct 2006 17:21:55 -0500, Tim Chase wrote:
With the caveat of the = mentioned in the subject-line (being
different from ==)...I haven't found any way to override
assignment in the general case.
Why would you want to do that?
For
Bruno Desthuilliers [EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
The current namespace object, of course.
Implementing a namespace as a Python object (ie, dict) is completely
optional and implementation dependent. For CPython, the local namespace of
a function is generally
Tim Chase wrote:
Can these operators be overloaded?
Yes.
With the caveat of the = mentioned in the subject-line (being
different from ==)...I haven't found any way to override
assignment in the general case. There might be some oddball way
to do it via property() but AFAIK, this only
Daniel Nogradi wrote:
Can these operators be overloaded?
If so. How?
http://www.python.org/doc/ref/numeric-types.html
HTH,
Daniel
Thanks everyone.
--
http://mail.python.org/mailman/listinfo/python-list
Can these operators be overloaded?
If so. How?
--
http://mail.python.org/mailman/listinfo/python-list
SpreadTooThin enlightened us with:
Can these operators be overloaded?
Yes.
If so. How?
Implement __add__, __sub__ etc. in the class that you want to be able
to add, subtract, etc.
Sybren
--
Sybren Stüvel
Stüvel IT - http://www.stuvel.eu/
--
Can these operators be overloaded?
If so. How?
http://www.python.org/doc/ref/numeric-types.html
HTH,
Daniel
--
http://mail.python.org/mailman/listinfo/python-list
Can these operators be overloaded?
Yes.
With the caveat of the = mentioned in the subject-line (being
different from ==)...I haven't found any way to override
assignment in the general case. There might be some oddball way
to do it via property() but AFAIK, this only applies to
Tim Chase wrote:
Can these operators be overloaded?
Yes.
With the caveat of the = mentioned in the subject-line (being
different from ==)...I haven't found any way to override
assignment in the general case. There might be some oddball way
to do it via property() but AFAIK, this only
Tim Chase enlightened us with:
With the caveat of the = mentioned in the subject-line (being
different from ==)...I haven't found any way to override
assignment in the general case.
Why would you want to do that?
Sybren
--
Sybren Stüvel
Stüvel IT - http://www.stuvel.eu/
--
With the caveat of the = mentioned in the subject-line (being
different from ==)...I haven't found any way to override
assignment in the general case.
Why would you want to do that?
For the same reason one would use property() to create
getter/setter functions for a particular variable--to
On Sat, 07 Oct 2006 17:21:55 -0500, Tim Chase wrote:
With the caveat of the = mentioned in the subject-line (being
different from ==)...I haven't found any way to override
assignment in the general case.
Why would you want to do that?
For the same reason one would use property() to
define new-style classes?
- Edward
Original Message Follows
From: Calvin Spealman [EMAIL PROTECTED]
Reply-To: [EMAIL PROTECTED]
To: Edward Waugh [EMAIL PROTECTED]
Subject: Re: Problem with operator overloading and inheritance in Python
Date: Mon, 18 Sep 2006 17:06:53 -0400
On 9/18
Consider the following code:
import sys
class FirstClass: def
__init__(self, value): self.data =
""> def __add__(self,
value): return
FirstClass(self.data + value) def
display(self): print
self.data
class
SecondClass(FirstClass): def __add__(self,
value): # Generalized version of
On 9/17/06, Edward A. Waugh [EMAIL PROTECTED] wrote:
Consider the following code:
import sys
class FirstClass:
def __init__(self, value):
self.data = value
def __add__(self, value):
return FirstClass(self.data + value)
def display(self):
print
Hello,
I just started out with python(
couple of weeks).
I have a query regarding Operator
Overloading
class c1:
def
__init__(self,value):
self.data
= "">
def
__add__ (self,operand2):
self.data
+= operand2
obj1 = c1(1)
obj1 + 10 # this works just fine
10 +
Mohit Bhatt wrote:
Hello,
I just started out with python( couple of weeks).
I have a query regarding Operator Overloading
class c1:
def __init__(self,value):
self.data = value
def __add__ (self,operand2
obj1 = c1(1)
obj1 + 10 # this works just fine
10 + obj1 # throws exception
Q. What do I have to do to make the following line work?
10 + obj1
http://docs.python.org/ref/numeric-types.html
You want to read the section on __radd__ (and it's other
Thanks a lot Fredrik and Tim for your help.
Cheers,
Mohit
--
http://mail.python.org/mailman/listinfo/python-list
Hi,
Is there any provision in python which allows me to make my own operators?
My problem is that I need to combine two dictonaries with their keys and I don't want to use any of the existing operators like '+','-','*'.
So is there a way I can make '**' or '~' as my operators to add two
Gurpreet Sachdeva wrote:
Hi,
Is there any provision in python which allows me to make my own operators?
My problem is that I need to combine two dictonaries with their keys and
I don't want to use any of the existing operators like '+','-','*'.
So is there a way I can make '**' or '~'
On 1 Aug 2005 05:12:47 -, Gurpreet Sachdeva
[EMAIL PROTECTED] wrote:
Hi,
Is there any provision in python which allows me to make my own operators?
My problem is that I need to combine two dictonaries with their keys and I
don't want to use any of the existing operators like
Hi Steve
I've been playing around with your two suggestions.
The Record class is an elegant solution. It doesn't however help in the
case where the class has the following general data structure (something
I should have stated originally):
class.config1 = param
class.config2 = param
Hi. I'm just starting to use python.
I am anxious about how best to set and access items one level down in a
data structure if I am using __setitem__ and __getitem__.
At the moment I can do
for a data structure Data:
object.Data = { 'one' : [1, 2, {}, 4],
'two' : [5, 6,
Anyone out there?
Criticism about the objective of my question, not just the execution,
gratefully received!
Basically, if I have a
class This:
def __init__(self, x, y):
self.x=x
self.y=y
self.data = {}
and then make all my setitem and getitem
Rory Campbell-Lange wrote:
Hi. I'm just starting to use python.
I am anxious about how best to set and access items one level down in a
data structure if I am using __setitem__ and __getitem__.
At the moment I can do
for a data structure Data:
object.Data = { 'one' : [1, 2, {}, 4],
On 25 Nov 2004 06:35:23 -0800, [EMAIL PROTECTED] (Sebastien Boisgerault) wrote:
Peter Maas [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED]...
Sebastien Boisgerault schrieb:
I wonder if the following quotation from the Python Reference Manual
(release 2.3.3) about operator
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