Re: how to use more than 1 __init__ constructor in a class ?
Steven D'Aprano wrote: On Wed, 22 Jun 2005 12:34:21 -0500, Rocco Moretti wrote: You could also turn __init__ into a dispatch fuction: #-- class myPointClass: def __init__(self, *args): if len(args) = 2: self.__init_two(*args) if len(args) == 3: self.__init_three(*args) Oh wow, so that's what I've been doing for years. Dispatching. And I thought I was just calling other functions :-) I think the distinction between just calling other functions and dispatching is that with dispatching, the function doesn't do any actual work by itself, but just hands off the work to a different function. http://www.c2.com/cgi/wiki?DispatchingForDummies That's the joys of a mostly self-taught programming knowledge: you miss out on all the buzzwords. Being mostly self taught myself, I have a tendancy to use infrequently encountered terms in related but technically inappropriate contexts, confusing the better informed people I deal with. ;-) -- http://mail.python.org/mailman/listinfo/python-list
Re: how to use more than 1 __init__ constructor in a class ?
Rocco Moretti wrote: Steven D'Aprano wrote: snip That's the joys of a mostly self-taught programming knowledge: you miss out on all the buzzwords. Being mostly self taught myself, I have a tendancy to use infrequently encountered terms in related but technically inappropriate contexts, confusing the better informed people I deal with. ;-) Indeed. I find I use even more buzzwords because I can just make up as many as I want. -- http://mail.python.org/mailman/listinfo/python-list
Re: how to use more than 1 __init__ constructor in a class ?
Singletoned wrote: Rocco Moretti wrote: Steven D'Aprano wrote: snip That's the joys of a mostly self-taught programming knowledge: you miss out on all the buzzwords. Being mostly self taught myself, I have a tendancy to use infrequently encountered terms in related but technically inappropriate contexts, confusing the better informed people I deal with. ;-) Indeed. I find I use even more buzzwords because I can just make up as many as I want. This thread 'branch' (humm, is this an appropriate term for the last few quotes, going to Steven's?) is soothing in reminding us we are not alone. That there is a sort of distributed 'Alma Mater' of the 'Teach-It-Yourself School of Computing', producing a virtual FOAF group (Is FOAF, Friend Of A Friend or Flock Of A Feather?) jm -- http://mail.python.org/mailman/listinfo/python-list
Re: how to use more than 1 __init__ constructor in a class ?
On Thursday 23 June 2005 10:31 am, Singletoned wrote: Rocco Moretti wrote: Steven D'Aprano wrote: snip That's the joys of a mostly self-taught programming knowledge: you miss out on all the buzzwords. Being mostly self taught myself, I have a tendancy to use infrequently encountered terms in related but technically inappropriate contexts, confusing the better informed people I deal with. ;-) Indeed. I find I use even more buzzwords because I can just make up as many as I want. As fun as that is ;-), it does make it hard to communicate. It seems to me that I spend a lot of time trying to figure out what buzzwords mean, only to find that 9/10ths of them are for things I've already done somewhere. Of course, that 10th one can be a doozy, metaclasses comes to mind. And it does make it easier to find help on problems, if you know what other people call them. -- Terry Hancock ( hancock at anansispaceworks.com ) Anansi Spaceworks http://www.anansispaceworks.com -- http://mail.python.org/mailman/listinfo/python-list
how to use more than 1 __init__ constructor in a class ?
hi people, can someone tell me, how to use a class like that* (or simulate more than 1 constructor) : #-- class myPointClass: def __init__(self, x=0, y=0): self.x = x self.y = y def __init__(self, x=0, y=0, z=0): self.__init__(self, x, y) self.z = z #-- tia people scott *this is not homework -- http://mail.python.org/mailman/listinfo/python-list
Re: how to use more than 1 __init__ constructor in a class ?
Hi Scott, can someone tell me, how to use a class like that* (or simulate more than 1 constructor) : One approach could be: class myPointClass: def __init__(self, **args): for k, v in args.items(): setattr(self, k, v) *this is not homework Just to be safe, I'll leave out the explanation :) Regards Steve On 6/22/05, scott [EMAIL PROTECTED] wrote: hi people, can someone tell me, how to use a class like that* (or simulate more than 1 constructor) : #-- class myPointClass: def __init__(self, x=0, y=0): self.x = x self.y = y def __init__(self, x=0, y=0, z=0): self.__init__(self, x, y) self.z = z #-- tia people scott *this is not homework -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: how to use more than 1 __init__ constructor in a class ?
scott wrote: can someone tell me, how to use a class like that* (or simulate more than 1 constructor) : #-- class myPointClass: def __init__(self, x=0, y=0): self.x = x self.y = y def __init__(self, x=0, y=0, z=0): self.__init__(self, x, y) self.z = z #-- Well for the example you used, multiple constructors are not needed. This will get you the same result as what I imagine you wanted the first example to do: class myPointClass: def __init__(self, x=0, y=0, z=0): self.x = x self.y = y self.z = z -- Michael Hoffman -- http://mail.python.org/mailman/listinfo/python-list
Re: how to use more than 1 __init__ constructor in a class ?
This recipe that I submitted to the Python Cookbook (http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/223611) describes a technique for doing this. I use the example of creating Color objects for plotting to a bitmap, using either R,G,andB values, or a single integer representing the RGB encoded value. This style you describe is a Java language artifact. If you have optional params, then these really don't represent different method signatures. In my color example, you truly have different signatures, either 3 integers representing color components, or a single encoded integer. -- Paul -- http://mail.python.org/mailman/listinfo/python-list
Re: how to use more than 1 __init__ constructor in a class ?
scott wrote: hi people, can someone tell me, how to use a class like that* (or simulate more than 1 constructor) : #-- class myPointClass: def __init__(self, x=0, y=0): self.x = x self.y = y def __init__(self, x=0, y=0, z=0): self.__init__(self, x, y) self.z = z #-- You might try: #-- class myPointClass: def __init__(self, x=0, y=0, z=None): self.x = x self.y = y if z is not None: self.z = z #-- You could also turn __init__ into a dispatch fuction: #-- class myPointClass: def __init__(self, *args): if len(args) = 2: self.__init_two(*args) if len(args) == 3: self.__init_three(*args) def __init_two(self, x=0, y=0): self.x = x self.y = y def __init_three(self, x=0, y=0, z=0): self.__init_two(x, y) self.z = z #-- But I would definitely recommend looking at your algorithm to determine if there is a better way to do what you want, that doesn't require an initilizer with two different signatures. -- http://mail.python.org/mailman/listinfo/python-list
Re: how to use more than 1 __init__ constructor in a class ?
You also could use a list to represent your data, then you get more
dimensions supported, e.g:
import math
class Point:
def __init__(self, *args):
self.points = list(args)
def dist(x, y):
if len(x.points) != len(y.points):
raise RuntimeError('dimensions not the same')
d = 0
for i in range(len(x.points)):
d += (x.points[i] - y.points[i])**2
return math.sqrt(d)
--
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Re: how to use more than 1 __init__ constructor in a class ?
Le 22 Jun 2005 11:44:09 -0700, [EMAIL PROTECTED] a écrit :
You also could use a list to represent your data, then you get more
dimensions supported, e.g:
import math
class Point:
def __init__(self, *args):
self.points = list(args)
def dist(x, y):
if len(x.points) != len(y.points):
raise RuntimeError('dimensions not the same')
d = 0
for i in range(len(x.points)):
d += (x.points[i] - y.points[i])**2
return math.sqrt(d)
My rewrite (same idea) :-)
class Point(object):
def __init__(self, *args):
self.coords = list(args) # or even args ?
def dist(self, other):
d2 = sum([ (c1-c2)*(c1-c2) for c1, c2 in zip(self.coords,
other.coords)])
return math.sqrt(d2)
--
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Re: how to use more than 1 __init__ constructor in a class ?
scott [EMAIL PROTECTED] wrote: hi people, can someone tell me, how to use a class like that* (or simulate more than 1 constructor) : #-- class myPointClass: def __init__(self, x=0, y=0): self.x = x self.y = y def __init__(self, x=0, y=0, z=0): self.__init__(self, x, y) self.z = z Python does not have the kind of polymorphism that C++ or Java has. There is only a single copy of each method (including __init__) for each class, but methods can take variable numbers of arguments, with default values. You probably want something like: def __init__(self, x=0, y=0, z=0): self.x = x self.y = y self.z = z You can call this with 0, 1, or 2 arguments, i.e. any of the following are legal: MyClass()# x, y, and z all get defaulted to 0 MyClass(1) # x=1, y and z both default to 0 MyClass(1, 2)# x=1, y=2, z defaults to 0 MyClass(1, 2, 3) # x=1, y=2, z=3 Once you get the hang of it, you'll understand just how brain-dead C++ and Java really are :-) Take a look at http://docs.python.org/ref/function.html for more details. -- http://mail.python.org/mailman/listinfo/python-list
Re: how to use more than 1 __init__ constructor in a class ?
Well one way to do this (not sure if it is the best way) is something like. class mypoint: def __init__(self, *args): len_args = len(args) print len_args if len_args == 0: self.x = 0 self.y = 0 self.z = 0 elif len_args =2 and len_args = 3: for i in range(len_args): if args[i] == None: args[i] = 0 #populating the list of args with defgault values if null(None) self.x = kargs[0] self.y = kargs[1] if len_args == 3: self.z = args[2] else: raise Invalid Input Now this is not looking for null input such as p = mypointclass(,,,) this is an invalid syntax error. Now there must be away to catch for the blanks but Iam not sure off the top of my head. hope that helps On 6/22/05, scott [EMAIL PROTECTED] wrote: hi people, can someone tell me, how to use a class like that* (or simulate more than 1 constructor) : #-- class myPointClass: def __init__(self, x=0, y=0): self.x = x self.y = y def __init__(self, x=0, y=0, z=0): self.__init__(self, x, y) self.z = z #-- tia people scott *this is not homework -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: how to use more than 1 __init__ constructor in a class ?
On Wed, 22 Jun 2005 12:34:21 -0500, Rocco Moretti wrote: scott wrote: hi people, can someone tell me, how to use a class like that* (or simulate more than 1 constructor) : #-- [snip] You could also turn __init__ into a dispatch fuction: #-- class myPointClass: def __init__(self, *args): if len(args) = 2: self.__init_two(*args) if len(args) == 3: self.__init_three(*args) Oh wow, so that's what I've been doing for years. Dispatching. And I thought I was just calling other functions :-) That's the joys of a mostly self-taught programming knowledge: you miss out on all the buzzwords. -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
