[Python-ideas] Proposal for an enhanced reload mechanism

[Chris Kaynor]

On Tue, Oct 19, 2010 at 12:17 PM, Peter Ingebretson <pingebre at yahoo.com>wrote:

> The builtin reload function is very useful for iterative development, but
> it is also limited.  Because references to types and functions in the old
> version of the module may persist after reloading, the builtin reload
> function is typically only useful in simple use cases.
>
> This is a proposal (pre-PEP?) for an enhanced reloading mechanism
> especially designed for iterative development:
>
>
> https://docs.google.com/document/pub?id=1GeVVC0pXTz1O6cK5mo-EaOJFqrL3PErO4okmHBlTeuw
>
> The basic plan is to use the existing cycle-detecting GC to remap
> references from objects in the old module to equivalent objects in the new
> module.
>
> I have a patch against the current 3.2 branch that adds the gc.remap
> function (and unit tests, etc...) but not any of the additional reloading
> functionality.  I have a separate prototype of the reloading module as well,
> but it only implements a portion of the proposal (one module at a time, and
> dicts/sets are not fixed up).
>
> A few questions:
>
> 1) Does this approach seem reasonable?  Has anyone tried something similar
> and run into unsolvable problems?
>
> 2) Would there be interest in a PEP for enhanced reloading?  I would be
> happy to rewrite the proposal in PEP form if people think it would be
> worthwhile.
>
> 3) Should I submit my gc.remap patch to the issue tracker?  Because the
> change to visitproc modifies the ABI I would like to get that portion of the
> proposal in before 3.2 goes final.  Since the bulk of the change is adding
> one method to the gc module I was hoping it might be accepted without
> requiring a PEP.
>
>
>
What happens if you change the __init__ or __new__ methods of an object or
if you change a class's metaclass? It seems like those types of changes
would be impossible to propagate to existing objects, and without
propagating them any changes to existing objects may (are likely?) to break
the object.


>
>
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