pickle

[Shi Mu]

I got a sample code and tested it but really can not understand the
use of pickle and dump:
[color=blue][color=green][color=darkred]
>>> import pickle
>>> f = open("try.txt", "w")
>>> pickle.dump(3.1 4, f)
>>> pickle.dump([1,2,3,4], f)
>>> f.close()[/color][/color][/color]

[marduk]

Re: pickle

On Mon, 2005-10-24 at 23:55 -0700, Shi Mu wrote:[color=blue]
> I got a sample code and tested it but really can not understand the
> use of pickle and dump:
>[color=green][color=darkred]
> >>> import pickle
> >>> f = open("try.txt", "w")
> >>> pickle.dump(3.1 4, f)
> >>> pickle.dump([1,2,3,4], f)
> >>> f.close()[/color][/color][/color]

The pickle module "serializes " python objects. You can "dump" a python
object that can later be loaded:
[color=blue][color=green][color=darkred]
>>> x = complex(2,3.5)
>>> f = open("cnumber.p ickle", "w")
>>> import pickle
>>> pickle.dump(x, f)
>>> f.close()
>>> y = pickle.load(fil e("cnumber.pick le", "r"))
>>> y[/color][/color][/color]
(2+3.5j)

[Shi Mu]

Re: pickle

what does the following code mean?

y = pickle.load(fil e("cnumber.pick le", "r"))

also, I can not understand "f" in pickle.dump(x, f)

On 10/25/05, marduk <usenet@marduk. letterboxes.org > wrote:[color=blue]
> On Mon, 2005-10-24 at 23:55 -0700, Shi Mu wrote:[color=green]
> > I got a sample code and tested it but really can not understand the
> > use of pickle and dump:
> >[color=darkred]
> > >>> import pickle
> > >>> f = open("try.txt", "w")
> > >>> pickle.dump(3.1 4, f)
> > >>> pickle.dump([1,2,3,4], f)
> > >>> f.close()[/color][/color]
>
> The pickle module "serializes " python objects. You can "dump" a python
> object that can later be loaded:
>[color=green][color=darkred]
> >>> x = complex(2,3.5)
> >>> f = open("cnumber.p ickle", "w")
> >>> import pickle
> >>> pickle.dump(x, f)
> >>> f.close()
> >>> y = pickle.load(fil e("cnumber.pick le", "r"))
> >>> y[/color][/color]
> (2+3.5j)
>
>
>[/color]

[Fredrik Lundh]

Re: pickle

Shi Mu wrote:
[color=blue]
> what does the following code mean?
>
> y = pickle.load(fil e("cnumber.pick le", "r"))[/color]

open the file "cnumber.pickle " for reading, pass the file handle to
the pickle.load function, and store the result in the "y" variable.
[color=blue]
> also, I can not understand "f" in pickle.dump(x, f)[/color]

the second argument to pickle is a file handle, opened for writing.
pickle.dump will save the "pickled data" to that file.

</F>

[Steve Holden]

Re: pickle

Shi Mu wrote:[color=blue]
> what does the following code mean?
>
> y = pickle.load(fil e("cnumber.pick le", "r"))
>[/color]
Take it by parts:

file("cnumber.p ickle", "r")

returns a file object as a result of opening the "cnumber.pickle " file,
which is presumably a pickle someone wrote earlier.

So

pickle.load(fil e("cnumber.pick le", "r"))

returns the first object stored in that pickle file.

[color=blue]
> also, I can not understand "f" in pickle.dump(x, f)
>[/color]
The beginning of the docs on pickle usage says:

"""dump( obj, file[, protocol[, bin]])

Write a pickled representation of obj to the open file object file."""

Isn't this reasopnably self-explanatory?

regards
Steve
[color=blue]
>[...][/color]

--
Steve Holden +44 150 684 7255 +1 800 494 3119
Holden Web LLC www.holdenweb.com
PyCon TX 2006 www.python.org/pycon/