Re: something wrong with isinstance
redbaron a écrit : Don't really sure, but try to define your class as new-style one. isinstance() works as well with classic classes. -- http://mail.python.org/mailman/listinfo/python-list
Re: something wrong with isinstance
maksym.ka...@gmail.com a écrit : Hi there. now i'm a complete newbie for python, and maybe my problem is stupid but i cannot solve it myself Others already addressed your problem (cf Paul and Diez answers). I'll just allow myself to point a couple other potential problems with your code: ##worldmap module class GeoMap: cells = [] activerow = 0 activecol = 0 Attributes defined at the class level are *class* attributes, shared by all instances of the class - that is, all instances will access the one same 'cells' list. Instance attributes are canonically created in the initialize method (__init__) that is automagically called on instanciation. IOW, you want to replace the above lines with: def __init__(self): self.cells = [] self.activerow = 0 self.activecol = 0 def addCell(self, acell): if len(self.cells) == 0: An empty list evals to False in a boolean context, so the above can be simply expressed as: if not self.cells: self.cells.append([]) self.activerow = 0 acell.col = self.activerow acell.row = self.activecol self.cells[self.activerow].append(acell) self.activecol += 1 def addRow(self): self.cells.append([]) self.activerow += 1; self.activecol = 0; class GeoMapCell: neighbours = (None, None, None, None, None, None, ) col = 0 row = 0 Same remark as above. You want to move all this code to the __init__ method. -- http://mail.python.org/mailman/listinfo/python-list
Re: something wrong with isinstance
On Feb 12, 10:49 am, redbaron ivanov.ma...@gmail.com wrote: Don't really sure, but try to define your class as new-style one. Like class GeoMap(object): ... Well, the OP said he was using Python 3.0, where all classes are new- style classes. But that brings up another very slight possibility, though not a very likely one in this case: the behavior of isinstance can be customized. It can happen unbeknownst to a user who subclasses a class that does that. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
Re: something wrong with isinstance
En Fri, 13 Feb 2009 08:07:58 -0200, Carl Banks pavlovevide...@gmail.com escribió: Well, the OP said he was using Python 3.0, where all classes are new- style classes. But that brings up another very slight possibility, though not a very likely one in this case: the behavior of isinstance can be customized. It can happen unbeknownst to a user who subclasses a class that does that. Really? I didn't know that -- how do you do that? -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
Re: something wrong with isinstance
Gabriel Genellina wrote: En Fri, 13 Feb 2009 08:07:58 -0200, Carl Banks pavlovevide...@gmail.com escribió: Well, the OP said he was using Python 3.0, where all classes are new- style classes. But that brings up another very slight possibility, though not a very likely one in this case: the behavior of isinstance can be customized. It can happen unbeknownst to a user who subclasses a class that does that. Really? I didn't know that -- how do you do that? class Type(type): ... def __instancecheck__(self, other): return True ... class A(metaclass=Type): pass ... class B: pass ... isinstance(B(), A) True See also http://www.python.org/dev/peps/pep-3119/#overloading-isinstance-and-issubclass I doubt that this is the source of the OP's troubles, though. Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: something wrong with isinstance
En Fri, 13 Feb 2009 08:43:03 -0200, Peter Otten __pete...@web.de escribió: Gabriel Genellina wrote: En Fri, 13 Feb 2009 08:07:58 -0200, Carl Banks pavlovevide...@gmail.com escribió: But that brings up another very slight possibility, though not a very likely one in this case: the behavior of isinstance can be customized. It can happen unbeknownst to a user who subclasses a class that does that. Really? I didn't know that -- how do you do that? class Type(type): ... def __instancecheck__(self, other): return True ... class A(metaclass=Type): pass ... class B: pass ... isinstance(B(), A) True See also http://www.python.org/dev/peps/pep-3119/#overloading-isinstance-and-issubclass Ah, ok. Isn't menctioned in the main documentation though. -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
Re: something wrong with isinstance
Gabriel Genellina wrote: En Fri, 13 Feb 2009 08:43:03 -0200, Peter Otten __pete...@web.de escribió: class Type(type): ... def __instancecheck__(self, other): return True ... class A(metaclass=Type): pass ... class B: pass ... isinstance(B(), A) True See also http://www.python.org/dev/peps/pep-3119/#overloading-isinstance-and-issubclass Ah, ok. Isn't menctioned in the main documentation though. Lack reported in http://bugs.python.org/issue5250 -- http://mail.python.org/mailman/listinfo/python-list
Re: something wrong with isinstance
On Feb 12, 11:53 am, maksym.ka...@gmail.com wrote: Hi there. now i'm a complete newbie for python, and maybe my problem is stupid but i cannot solve it myself i have an object of class GeoMap which contains lists with objects of GeoMapCell (i will not explain what they should do, hope its not important). Then i want to serialize these objects to json notation. So i imported json module and as shown in docs for it extended JSONEncoder class. Look at the code below ##main module from worldmap import GeoMap, GeoMapCell import testdata import json class GeoMapEncoder(json.JSONEncoder): def default(self, obj): if isinstance(obj, GeoMap): return None return json.JSONEncoder.default(self, obj) def main(): print(json.dumps(2 + 5j, cls=ComplexEncoder)) geomap = testdata.createTestMap() print(json.dumps(geomap, cls=GeoMapEncoder)) pass if __name__ == '__main__': main() === ##worldmap module class GeoMap: cells = [] activerow = 0 activecol = 0 def addCell(self, acell): if len(self.cells) == 0: self.cells.append([]) self.activerow = 0 acell.col = self.activerow acell.row = self.activecol self.cells[self.activerow].append(acell) self.activecol += 1 def addRow(self): self.cells.append([]) self.activerow += 1; self.activecol = 0; class GeoMapCell: neighbours = (None, None, None, None, None, None, ) col = 0 row = 0 The problem is in here. class GeoMapEncoder(json.JSONEncoder): def default(self, obj): if isinstance(obj, GeoMap): ## === isinstance doesnot work as i expected return None return json.JSONEncoder.default(self, obj) Though obj is object of GeoMap class, isinstance returns False. Where was i mistaken. If i shouldn't use isinstance, then what function would check class of object? Oh, maybe its important. I'm working on WinXP SP3, Python 3.0, IDE - PyScript Here's a crazy idea out of left field. Just before calling isinstance, why not try: print(type(obj)) print(str(obj)) This may illuminate the unexpected behavior, you'll find out just what obj has in it. -- Paul -- http://mail.python.org/mailman/listinfo/python-list
Re: something wrong with isinstance
Here's a crazy idea out of left field. Just before calling isinstance, why not try: print(type(obj)) print(str(obj)) This may illuminate the unexpected behavior, you'll find out just what obj has in it. -- Paul Well the output of print(type(obj)) print(str(obj)) was class 'worldmap.GeoMap' worldmap.GeoMap object at 0x01DD17B0 Just looks well, isn't it? i have no idea what's wrong -- http://mail.python.org/mailman/listinfo/python-list
Re: something wrong with isinstance
Don't really sure, but try to define your class as new-style one. Like class GeoMap(object): ... -- http://mail.python.org/mailman/listinfo/python-list
Re: something wrong with isinstance
On 12 фев, 21:49, redbaron ivanov.ma...@gmail.com wrote: Don't really sure, but try to define your class as new-style one. Like class GeoMap(object): ... Sorry, it didn't work -- http://mail.python.org/mailman/listinfo/python-list
Re: something wrong with isinstance
On Feb 12, 12:26 pm, maksym.ka...@gmail.com wrote: Well the output of print(type(obj)) print(str(obj)) was class 'worldmap.GeoMap' worldmap.GeoMap object at 0x01DD17B0 Just looks well, isn't it? i have no idea what's wrong So then how do you know isinstance is evaluating to False? And why do you return None if it evals to True? Can you drop a print command inside the if block just before returning None, and another print just before returning the default default? I also would recommend using a debugger like winpdb when in a spot like this - despite the name, it is not Windows-only, and you can step through this code and evaluate variables and expressions inline. -- Paul -- http://mail.python.org/mailman/listinfo/python-list
Re: something wrong with isinstance
maksym.ka...@gmail.com schrieb: Hi there. now i'm a complete newbie for python, and maybe my problem is stupid but i cannot solve it myself i have an object of class GeoMap which contains lists with objects of GeoMapCell (i will not explain what they should do, hope its not important). Then i want to serialize these objects to json notation. So i imported json module and as shown in docs for it extended JSONEncoder class. Look at the code below ##main module from worldmap import GeoMap, GeoMapCell import testdata import json class GeoMapEncoder(json.JSONEncoder): def default(self, obj): if isinstance(obj, GeoMap): return None return json.JSONEncoder.default(self, obj) def main(): print(json.dumps(2 + 5j, cls=ComplexEncoder)) geomap = testdata.createTestMap() print(json.dumps(geomap, cls=GeoMapEncoder)) pass if __name__ == '__main__': main() === ##worldmap module class GeoMap: cells = [] activerow = 0 activecol = 0 def addCell(self, acell): if len(self.cells) == 0: self.cells.append([]) self.activerow = 0 acell.col = self.activerow acell.row = self.activecol self.cells[self.activerow].append(acell) self.activecol += 1 def addRow(self): self.cells.append([]) self.activerow += 1; self.activecol = 0; class GeoMapCell: neighbours = (None, None, None, None, None, None, ) col = 0 row = 0 The problem is in here. class GeoMapEncoder(json.JSONEncoder): def default(self, obj): if isinstance(obj, GeoMap): ## === isinstance doesnot work as i expected return None return json.JSONEncoder.default(self, obj) Though obj is object of GeoMap class, isinstance returns False. Where was i mistaken. If i shouldn't use isinstance, then what function would check class of object? Oh, maybe its important. I'm working on WinXP SP3, Python 3.0, IDE - PyScript I think you have a common problem here that occurs when using a script with more that non-trivial contents as main-script. What happens is this: you have a __main__.GeoMap, which is the one tested against in isinstance. *And* you have a mainmodule.GeoMap (replace mainmodule with the actual name) that is imported used from the other module. A simple testscript illustrates the issue: ### test.py class Foo(object): pass if __name__ == __main__: import test print Foo == test.Foo Run it from inside the directory you saved it in. To work around this issue, simply create a bootstrap-main-module that has not much in it. Diez -- http://mail.python.org/mailman/listinfo/python-list
