pickling lambdas?

[gong]

hi

i would like to pickle a lambda; according to the library docs in 2.3,
i believe this shouldnt be possible, since a lambda is not a function
defined at the top level of a module (?)

however, upon google searching for "python lambda pickle" i find 2
posts, one including gvr, which apparently demonstrate that this was
being attempted and even suggest that it is feasible. has this become
available yet, or will it be soon?

thanks
gong

 

[John Roth]

hi

i would like to pickle a lambda; according to the library docs in 2.3,
i believe this shouldnt be possible, since a lambda is not a function
defined at the top level of a module (?)

however, upon google searching for "python lambda pickle" i find 2
posts, one including gvr, which apparently demonstrate that this was
being attempted and even suggest that it is feasible. has this become
available yet, or will it be soon?

thanks
gong

Why do you want to do this? According to the docs, all that
is saved for a function or a class is the name. Code, data and
so forth is not saved, so it makes no sense to try to pickle
a lambda unless you've bound it to a name at the module
level. See 3.14.4 (Python 2.3.3 Library Reference.)

If you really want to serialize a function's code, look at
the marshal module.

John Roth

 

[John J. Lee]

i would like to pickle a lambda; according to the library docs in 2.3,
i believe this shouldnt be possible, since a lambda is not a function
defined at the top level of a module (?)
Yes.


however, upon google searching for "python lambda pickle" i find 2
posts, one including gvr, which apparently demonstrate that this was
being attempted and even suggest that it is feasible. has this become

[...]

No, read it again. What you found was Guido figuring out how to
*prevent* people pickling lambdas. Functions are pickled by saving
the function name. Lambdas have no function name, so pickle complains
if you try to pickle them.


John

 

[Paul Rubin]

Why do you want to do this? According to the docs, all that
is saved for a function or a class is the name. Code, data and
so forth is not saved, so it makes no sense to try to pickle
a lambda unless you've bound it to a name at the module level.

I think the idea may be to pickle a closure, to save the data inside
it. I do remember some mention about pickling generators. Anyway, in
Python 2.x the closest you can come to that is pickling class
instances.

 

[John Roth]

I think the idea may be to pickle a closure, to save the data inside
it. I do remember some mention about pickling generators. Anyway, in
Python 2.x the closest you can come to that is pickling class
instances.

That ought to work as long as you unpickle it into the same module
so you can get the original class definition.

John Roth