I was interested in playing around with Decimal and
subclassing it. For example, if I wanted a special
class to permit floats to be automatically converted
to strings.
from decimal import Decimal
class MyDecimal(Decim al):
def __init__(self, value):
if isinstance(valu e, float):
... initialize using str(float) ...
In the classic days, I would have added something
like this to MyDecimal __init__:
Decimal.__init_ _(self, str(value))
But I'm unfamiliar with the __new__ protocol.
Jeff Bauer
Rubicon, Inc. 3 2236 jb****@rubic.co m wrote: I was interested in playing around with Decimal and subclassing it. For example, if I wanted a special class to permit floats to be automatically converted to strings.
from decimal import Decimal
class MyDecimal(Decim al): def __init__(self, value): if isinstance(valu e, float): ... initialize using str(float) ...
In the classic days, I would have added something like this to MyDecimal __init__:
Decimal.__init_ _(self, str(value))
But I'm unfamiliar with the __new__ protocol.
__new__ is called to create a new instance of the class. It is a
staticmethod that gets passed as its first parameter the class to be
created. You should be able to do something like[1]:
py> import decimal
py> class MyDecimal(decim al.Decimal):
.... def __new__(cls, value):
.... if isinstance(valu e, float):
.... value = str(value)
.... return super(MyDecimal , cls).__new__(cl s, value)
....
py> MyDecimal(3.0)
Decimal("3.0")
STeVe
[1] If you're really afraid of super for some reason, you can replace
the line:
return super(MyDecimal , cls).__new__(cl s, value)
with
return decimal.Decimal .__new__(cls, value)
STeVe,
Thanks for the response. Very clear.
yea-though-I-walk-thru-the-valley-of-__new__-I-will-fear-no-super-ly
y'rs,
-Jeff This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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