Subclassing array.array

[Gus Tabares]

Hello all,

I'm trying to subclass array.array but having problems with a default
parameter in the init constructor. Example:

import array

class TestClass(array.array):
def __init__(self, array_type = "B"):
array.array(array_type)

temp = TestClass()

Traceback (most recent call last):
File "<pyshell#1>", line 1, in ?
temp = TestClass()
TypeError: array() takes at least 1 argument (0 given)

I think there is something that I'm not understanding here. Any help
is appreciated.
Thanks,
Gus

[Larry Bates]

I think you meant to write:
class TestClass(array.array):
def __init__(self, array_type = "B"):
array.array(self, array_type)

Note that your "default" got gobbled upwhen
array.array was looking for first argument
to be self.

HTH,
Larry Bates
Syscon, Inc.
"Gus Tabares" <gu********@verizon.net> wrote in message
news:c4**************************@posting.google.c om...

Hello all,

I'm trying to subclass array.array but having problems with a default
parameter in the init constructor. Example:

import array

class TestClass(array.array):
def __init__(self, array_type = "B"):
array.array(array_type)

temp = TestClass()

Traceback (most recent call last):
File "<pyshell#1>", line 1, in ?
temp = TestClass()
TypeError: array() takes at least 1 argument (0 given)

I think there is something that I'm not understanding here. Any help
is appreciated.
Thanks,
Gus

[Peter Otten]

Gus Tabares wrote:

I'm trying to subclass array.array but having problems with a default
parameter in the init constructor. Example:

import array

class TestClass(array.array):
def __init__(self, array_type = "B"):
array.array(array_type)

temp = TestClass() Traceback (most recent call last):
File "<pyshell#1>", line 1, in ?
temp = TestClass()
TypeError: array() takes at least 1 argument (0 given)

I think there is something that I'm not understanding here. Any help
is appreciated.

Seems like the argument check happens in __new__(). Try overriding that
instead:

class Array(array.array): .... def __new__(cls, tc="B"):
.... return array.array.__new__(cls, tc)
.... a = Array()
a array('B') type(a) <class '__main__.Array'>

Peter