Unbound Method Error

[Chris Rebert]

On Mon, Jun 8, 2009 at 7:23 PM, lczancanella<lczancanella at gmail.com> wrote:
> Hi, i am brand new in Python, so sorry if this question is too basic,
> but i have tried a lot and dont have success... I have the following
> code...
>
> class Funcoes:
>    def CifradorDeCesar(mensagem, chave, funcao):
>        mensagem_encriptada=''
>        if funcao == 1:
>            for byte in mensagem:
>                if byte.isalpha():
>                    byte_encriptado=chr(ord(byte)+chave)
>                    if byte.isupper() and ord(byte_encriptado) > 90:
>                        byte_encriptado=chr(ord(byte_encriptado)-26)
>                    if byte.islower() and ord(byte_encriptado) > 122:
>                        byte_encriptado=chr(ord(byte_encriptado)-26)
>                else:
>                    byte_encriptado=byte
>                mensagem_encriptada+=byte_encriptado
>        else:
>            for byte in mensagem:
>                if byte.isalpha():
>                    byte_encriptado=chr(ord(byte)-chave)
>                    if byte.isupper() and ord(byte_encriptado) < 65:
>                        byte_encriptado=chr(ord(byte_encriptado)+26)
>                    if byte.islower() and ord(byte_encriptado) < 97:
>                        byte_encriptado=chr(ord(byte_encriptado)+26)
>                else:
>                    byte_encriptado=byte
>                mensagem_encriptada+=byte_encriptado
>
>        return mensagem_encriptada
>
> class MC(Funcoes, type):
>    def __init__(cls, clsname, bases, ns):
>        def addtrace(f):
>            def t(self, *args, **kwargs):
>                for att in self.__crypt__:
>                    atribcripto = getattr(self, att)
>                    atribdescripto = Funcoes.CifradorDeCesar
> (atribcripto, 3, 2)
>                    setattr(self, att, atribdescripto)
>                ret = f(self, *args, **kwargs)
>                for att in self.__crypt__:
>                    atribdescripto = getattr(self, att)
>                    atribcripto = Funcoes.CifradorDeCesar
> (atribdescripto, 3, 1)
>                    setattr(self, att, atribcripto)
>                # aqui seta __signature__ vazio, assina e atribui
> __signature__
>                return ret
>            return t
>        from types import FunctionType
>        for name,obj in ns.items():
>            if type(obj) == FunctionType:
>                setattr(cls, name, addtrace(ns[name]))
>
> class C():
>
>    __metaclass__ = MC
>    __crypt__ = ["_a", "_b"]
>
>    _a = 1
>    _b = 2
>
>    def add(self, a, b):
>        _a = a
>        _b = b
>        return a+b
>
> then i call
>
>>>> i = C()
>>>> i.add(2,2)
>
> and the error:
>
> File "C:\Users\Junior\Desktop\Python\T2.py", line 37, in t
>    atribdescripto = Funcoes.CifradorDeCesar(atribcripto, 3, 2)
> TypeError: unbound method CifradorDeCesar() must be called with
> Funcoes instance as first argument (got int instance instead)

`CifradorDeCesar` is an instance method of the class `Funcoes`, and
thus can only be used on instances of the class, *NOT the class
itself*.
Since it appears to be just a normal function (as suggested by the
name of the class and the fact that it lacks `self` as its first
parameter), you should scrap the class entirely and just define
`CifradorDeCesar` in the toplevel body of the module.
Unlike Java, it is *not* good Python style to unnecessarily cram
functions into classes.

Cheers,
Chris
-- 
http://blog.rebertia.com