Greg Ward wrote:
On 05 March 2005, Nick Coghlan said:
Steven Bethard has put together some text to add __new__ to the list of
Basic Customisation methods in the language reference. Would one of the
documentation folks care to take a look at it?
I've tried to tighten up the text there and hopefully make it a smidgeon
clearer and more accurate. Here's my best effort:
__new__(cls[, ...])
Called to create a new instance of class 'cls'. __new__()
is a static method (special-cased so you need not declare it
as such) that takes the class to create an instance of as
the first argument. The remaining arguments are those
passed to the object constructor expression. The return
value of __new__() should be the new object instance.
Just to offer alternatives:
__new__(cls[, ...])
__new__() is a static method (special-cased so you need
not declare it as such) whose fist argumen is the class
of which a new instance is required. The remaining arguments
are those passed to the object constructor expression (the
call to the class). The return value of __new__() should be
the new instance object, which is not constrained to be of
type 'cls'.
Typical usage is to create a new instance of the class by
invoking the superclass's __new__() method using
"super(currentclass, cls).__new__([...])" with appropriate
arguments, modifying the returned instance if necessary, and
then returning it. If the returned value is an instance of
'cls', its __init__() will be invoked like
"__init__(self[, ...])", where the extra arguments are the
same as were passed to __new__().
Typical usage creates a new instance of the required
class by invoking the superclass's __new__() method
using "super(currentclass, cls).__new__(...)" with
appropriate argumnents and then modifying the newly-
created instance as necessary before returning it.
If __new__() returns an instance of 'cls' then the new
instance's __init__() method will be called with the
instance itself as the first argument and the remaining
arguments being the second and subsequent arguments to
__new__().
You do need not to return an instance of 'cls', but if you
do not, the new instance's __init__() method will not be
invoked.
If __new__() does not return an instance of 'cls' then the
new instance's __init__() method will not be invoked.
__new__() is intended mainly to allow subclasses of
immutable types (like int, str, or tuple) to customize
instance creation.
Feedback welcome. Has anyone volunteered to render this in LaTeX yet?
If not, I might.
Greg
I decided some time ago that documenting Python in LaTex wasn't my forte ...
regards
Steve
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