Need help with syntax on inheritance.

[SpreadTooThin]

If you are deriving a new class from another class,
that you must (I assume) know the initializer of the other class.

So in myClass

import array
class myClass(arrary. array):
def __init__(self, now here I need to put array's constructor
parameters..., then mine):
array.array.__i nit__(self, typecode[, initializer])
self.mine = mine

So I'm confused...
array has a typecode parameter and an optional initiializer...
So could you help me with the class construction here please?

[jordan.nick@gmail.com]

Re: Need help with syntax on inheritance.


SpreadTooThin wrote:

If you are deriving a new class from another class,
that you must (I assume) know the initializer of the other class.
>
So in myClass
>
import array
class myClass(arrary. array):
def __init__(self, now here I need to put array's constructor
parameters..., then mine):
array.array.__i nit__(self, typecode[, initializer])
self.mine = mine
>
So I'm confused...
array has a typecode parameter and an optional initiializer...
So could you help me with the class construction here please?

Lookup *args and **kargs in the python reference manual.

[Calvin Spealman]

Re: Need help with syntax on inheritance.

On 3 Oct 2006 19:09:53 -0700, SpreadTooThin <bjobrien62@gma il.comwrote:

If you are deriving a new class from another class,
that you must (I assume) know the initializer of the other class.
>
So in myClass
>
import array
class myClass(arrary. array):
def __init__(self, now here I need to put array's constructor
parameters..., then mine):
array.array.__i nit__(self, typecode[, initializer])
self.mine = mine
>
So I'm confused...
array has a typecode parameter and an optional initiializer...
So could you help me with the class construction here please?

If you need to take the same parameters as your super-class, and it
includes optional positional parameters, then simply call with
keywords to avoid the optional parameter:

myClass(typecod e, mine=something)

It has less to do with defining the parameters than calling the function.

[Peter Otten]

Re: Need help with syntax on inheritance.

SpreadTooThin wrote:

If you are deriving a new class from another class,
that you must (I assume) know the initializer of the other class.
>
So in myClass
>
import array
class myClass(arrary. array):
def __init__(self, now here I need to put array's constructor
parameters..., then mine):
array.array.__i nit__(self, typecode[, initializer])
self.mine = mine
>
So I'm confused...
array has a typecode parameter and an optional initiializer...
So could you help me with the class construction here please?

Normally you would do

# won't work
class Array(array.arr ay):
def __init__(self, typecode, initalizer=(), mine=None):
array.array.__i nit__(self, typecode, initializer)
self.mine = mine

However, array.array is a bit harder to subclass:

# should work
class Array(array.arr ay):
def __new__(cls, typecode, initializer=(), mine=None):
return array.array.__n ew__(cls, typecode, initializer)
def __init__(self, typecode, initializer=(), mine=None):
array.array.__i nit__(self, typecode, initializer)
self.mine = mine

See if you can get away by making the array an attribute of your class
instead.

Peter

[SpreadTooThin]

Re: Need help with syntax on inheritance.


Peter Otten wrote:

SpreadTooThin wrote:
>

If you are deriving a new class from another class,
that you must (I assume) know the initializer of the other class.

So in myClass

import array
class myClass(arrary. array):
def __init__(self, now here I need to put array's constructor
parameters..., then mine):
array.array.__i nit__(self, typecode[, initializer])
self.mine = mine

So I'm confused...
array has a typecode parameter and an optional initiializer...
So could you help me with the class construction here please?

>
Normally you would do
>
# won't work
class Array(array.arr ay):
def __init__(self, typecode, initalizer=(), mine=None):
array.array.__i nit__(self, typecode, initializer)
self.mine = mine
>
However, array.array is a bit harder to subclass:
>
# should work
class Array(array.arr ay):
def __new__(cls, typecode, initializer=(), mine=None):
return array.array.__n ew__(cls, typecode, initializer)
def __init__(self, typecode, initializer=(), mine=None):
array.array.__i nit__(self, typecode, initializer)
self.mine = mine
>
See if you can get away by making the array an attribute of your class
instead.
>

Thanks.
the =() syntax indicates what?
Just slightly off topic here but if Array had a bunch of initializers
of its own,
must all the 'optional' parameters be on the right.. ie the last
parameters?

Peter

[Peter Otten]

Re: Need help with syntax on inheritance.

SpreadTooThin wrote:

the =() syntax indicates what?

No special syntax, just an empty tuple as a default parameter.
In this case I could have used an empty list, too, but I thought I'd spare
you the dangers of mutable default values as explained here:

http://www.python.org/doc/faq/general/#id53

Just slightly off topic here but if Array had a bunch of initializers
of its own, must all the 'optional' parameters be on the right.. ie the
last parameters?

Yes.

Peter