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dump a multi dimensional dictionary

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  dump a multi dimensional dictionary cerr <ron.eggler@gmail.com> - 2013-07-26 13:21 -0700
    Re: dump a multi dimensional dictionary John Gordon <gordon@panix.com> - 2013-07-26 21:00 +0000
    RE: dump a multi dimensional dictionary "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2013-07-26 20:40 +0000
    Re: dump a multi dimensional dictionary Chris Angelico <rosuav@gmail.com> - 2013-07-27 00:33 +0100
    Re: dump a multi dimensional dictionary Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-27 02:54 +0000

#51320 — dump a multi dimensional dictionary

Hi,

Can I somehow use pickle.dump() to store a dictionary of lists to a file?
I tried this:

    >>> import pickle
    >>> mylist = []
    >>> mydict = {}
    >>> mylist = '1','2'
    >>> mydict['3'] = mylist
    >>> fhg = open ("test", 'w')
    >>> pickle.dump(fhg,mydict)
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
      File "/usr/lib/python2.7/pickle.py", line 1370, in dump
        Pickler(file, protocol).dump(obj)
      File "/usr/lib/python2.7/pickle.py", line 203, in __init__
        self.write = file.write
    AttributeError: 'dict' object has no attribute 'write'
    >>> print mydict
    {'3': ('1', '2')}

or should I just write my own dump function that can hanle thiS?

Please advise!

Thanks,
Ron

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#51321

In <efdc6f6b-c061-4d3d-9d02-c397f8953d93@googlegroups.com> cerr <ron.eggler@gmail.com> writes:

> Can I somehow use pickle.dump() to store a dictionary of lists to a file?
> I tried this:

>     >>> import pickle
>     >>> mylist = []
>     >>> mydict = {}
>     >>> mylist = '1','2'
>     >>> mydict['3'] = mylist
>     >>> fhg = open ("test", 'w')
>     >>> pickle.dump(fhg,mydict)
>     Traceback (most recent call last):
>       File "<stdin>", line 1, in <module>
>       File "/usr/lib/python2.7/pickle.py", line 1370, in dump
>         Pickler(file, protocol).dump(obj)
>       File "/usr/lib/python2.7/pickle.py", line 203, in __init__
>         self.write = file.write
>     AttributeError: 'dict' object has no attribute 'write'
>     >>> print mydict
>     {'3': ('1', '2')}

> or should I just write my own dump function that can hanle thiS?

I think you have the arguments to pickle.dump() in the wrong order.
The data to be dumped should come first, then the file object.

-- 
John Gordon                   A is for Amy, who fell down the stairs
gordon@panix.com              B is for Basil, assaulted by bears
                                -- Edward Gorey, "The Gashlycrumb Tinies"

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#51322

cerr wrote:
> Hi,
> 
> Can I somehow use pickle.dump() to store a dictionary of lists to a file?
> I tried this:
> 
>     >>> import pickle
>     >>> mylist = []
>     >>> mydict = {}
>     >>> mylist = '1','2'
>     >>> mydict['3'] = mylist
>     >>> fhg = open ("test", 'w')
>     >>> pickle.dump(fhg,mydict)
>     Traceback (most recent call last):
>       File "<stdin>", line 1, in <module>
>       File "/usr/lib/python2.7/pickle.py", line 1370, in dump
>         Pickler(file, protocol).dump(obj)
>       File "/usr/lib/python2.7/pickle.py", line 203, in __init__
>         self.write = file.write
>     AttributeError: 'dict' object has no attribute 'write'
>     >>> print mydict
>     {'3': ('1', '2')}
> 
> or should I just write my own dump function that can hanle thiS?
> 
> Please advise!
> 
> Thanks,
> Ron

I think you have the parameters for dump backwards.

According to API http://docs.python.org/2/library/pickle.html#pickle.dump
the format is: pickle.dump(obj, file, protocol=None)

Which means you need to use: pickle.dump(mydict, fhg)


Ramit



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#51325

On Fri, Jul 26, 2013 at 9:21 PM, cerr <ron.eggler@gmail.com> wrote:
>     >>> mylist = []
>     >>> mydict = {}
>     >>> mylist = '1','2'


Side point: mylist is no longer a list, it's a tuple. I don't think
pickle has problems with tuples, but it's worth noting that
difference.

ChrisA

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#51330

On Fri, 26 Jul 2013 13:21:47 -0700, cerr wrote:

> or should I just write my own dump function that can hanle thiS?
> 
> Please advise!

Given the choice between reading the documentation to pickle.dump:

help(pickle.dump)


or spending the next month writing a replacement for pickle, testing it, 
debugging it, going through revision after revision to try to bring it to 
the same level of maturity as pickle, which would you prefer? 

:-)


-- 
Steven

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