Tags: 4couple, __init__, a7self, b1231, class, disk, etci, foodef, lists, members, object, programming, python, sayclass, self, tuples, writing
Writing Object Data to Disk
On Programmer » Python
5,331 words with 9 Comments; publish: Mon, 28 Apr 2008 05:51:00 GMT; (20046.88, « »)
Hello,
I have a Python class with data members, say:
class Foo:
def __init__(self):
self.a=7
self.b[]={1,3,4}
#couple of more lists, tuples, etc
I would like to know if "Pickling" the class object is the only way of
writing it to disk for persistent storage. Also, do we have a concept
similar to "array of objects" in Python? The number of objects is only
known at "run-time".
Thanks,
Amit Kumar Saha
me blogs.python.itags.org. http://amitksaha.blogspot.com
URL:http://amitsaha.in.googlepages.com
http://python.itags.org/q_python_100656.html
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- 9 Comments
- In message <mailman.914.1190444082.2658.python-list.python.itags.org.python.org>, Amit Kumar
Saha wrote:
> I would like to know if "Pickling" the class object is the only way of
> writing it to disk for persistent storage.
Wouldn't it be better to use a language-independent data representation that
wasn't tied to Python? Also tying your external data representation to your
internal program structure (objects) makes it harder to change the program
in future.
#1; Mon, 28 Apr 2008 05:53:00 GMT
- "Amit Kumar Saha" <da...o.in> wrote:
> I would like to know if "Pickling" the class object is the only way of
> writing it to disk for persistent storage.
look at marshall and shelve
>.............................................Also, do we have a[/colo
r]
concept
> similar to "array of objects" in Python? The number of objects is only
> known at "run-time".
I would use a list
- Hendrik
#2; Mon, 28 Apr 2008 05:54:00 GMT
- Amit Kumar Saha wrote:
> I have a Python class with data members, say:
> class Foo:
> def __init__(self):
> self.a=7
> self.b[]={1,3,4}
^^
This is invalid syntax.
> I would like to know if "Pickling" the class object is the only
> way of writing it to disk for persistent storage.
It isn't. Every means of serialisation works, but pickling is
especially convenient if you only use Python.
> Also, do we have a concept similar to "array of objects" in
> Python?
You can put all objects in lists, be it a string, an integer or some
complex class instance.
> The number of objects is only known at "run-time".
class and function definitions also happen at runtime. I suggest you
worked through the Python tutorial to get a deeper insight in
Python's concepts.
Regards,
Bjrn
BOFH excuse #89:
Electromagnetic energy loss
#3; Mon, 28 Apr 2008 05:55:00 GMT
- On 22/09/2007 7:16 PM, Bjoern Schliessmann wrote:
> Amit Kumar Saha wrote:
> ^^
> This is invalid syntax.
So are the braces.
#4; Mon, 28 Apr 2008 05:56:00 GMT
- On Sat, 22 Sep 2007 17:13:14 +0530, Amit Kumar Saha wrote:
> BTW, do we have something like array of objects here?
Like someone already said: lists.
Ciao,
Marc 'BlackJack' Rintsch
#5; Mon, 28 Apr 2008 05:57:00 GMT
- "Lawrence D'Oliveiro" <ldo.python.itags.org.g-central.gen.new_zealand> wrote in message
news:fd300j$ag$1.python.itags.org.lust.ihug.co.nz...
> In message <mailman.922.1190461411.2658.python-list.python.itags.org.python.org>, Amit
> Kumar
> Saha wrote:
>
> Even so, ignoring the issue of future changes is folly.
Can't Python tie into a DB such as MySQL?
I'm a C++ programmer currently, but have programmed in many many languages,
I only use Python to help someone work on an internet service and to modify
some Python code for OpenRPG, so I'm not real familiar with all Python can
actually do.
#6; Mon, 28 Apr 2008 05:58:00 GMT
- > I would like to know if "Pickling" the class object is the only way of
> writing it to disk for persistent storage. Also, do we have a concept
> similar to "array of objects" in Python? The number of objects is only
> known at "run-time".
Have a look at YAML.
http://freshmeat.net/projects/syck/
Also it is possible to persist python data to and from XML. See
xml.marshal.generic.dumps
#7; Mon, 28 Apr 2008 05:59:00 GMT
- Amit Kumar Saha wrote:
> Actually, language independence is really not a consideration here. I am
> happy at having it tied to Python :-)
> BTW, do we have something like array of objects here?
In numpy, one can have a multi-dimensional array of objects. It would
be good to have this notion implemented in Python itself.
Colin W.
#8; Mon, 28 Apr 2008 06:00:00 GMT
- David a crit :
> Have a look at YAML.
> http://freshmeat.net/projects/syck/
> Also it is possible to persist python data to and from XML. See
> xml.marshal.generic.dumps
or JSON...
#9; Mon, 28 Apr 2008 06:01:00 GMT