reading files into dicts

[rbt]

What's a good way to write a dictionary out to a file so that it can be
easily read back into a dict later? I've used realines() to read text
files into lists... how can I do the same thing with dicts? Here's some
sample output that I'd like to write to file and then read back into a dict:

{'.\\sync_pics. py': 1135900993, '.\\file_histor y.txt': 1135900994,
'.\\New Text Document.txt': 1135900552}

[Giovanni Bajo]

Re: reading files into dicts

rbt wrote:
[color=blue]
> What's a good way to write a dictionary out to a file so that it can
> be easily read back into a dict later? I've used realines() to read
> text
> files into lists... how can I do the same thing with dicts? Here's
> some sample output that I'd like to write to file and then read back
> into a dict:
>
> {'.\\sync_pics. py': 1135900993, '.\\file_histor y.txt': 1135900994,
> '.\\New Text Document.txt': 1135900552}[/color]


[color=blue][color=green][color=darkred]
>>> d = {'.\\sync_pics. py': 1135900993, '.\\file_histor y.txt': 1135900994,[/color][/color][/color]
.... '.\\New Text Document.txt': 1135900552}[color=blue][color=green][color=darkred]
>>> file("foo", "w").write(repr (d))
>>> data = file("foo").rea d()
>>> data[/color][/color][/color]
"{'.\\\\sync_pi cs.py': 1135900993, '.\\\\file_hist ory.txt': 1135900994,
'.\\\\New Text Document.txt': 1135900552}"[color=blue][color=green][color=darkred]
>>> d = eval(data)
>>> d[/color][/color][/color]
{'.\\sync_pics. py': 1135900993, '.\\file_histor y.txt': 1135900994, '.\\New Text
Document.txt': 1135900552}

--
Giovanni Bajo

[limodou]

Re: reading files into dicts

2005/12/30, rbt <rbt@athop1.ath .vt.edu>:[color=blue]
> What's a good way to write a dictionary out to a file so that it can be
> easily read back into a dict later? I've used realines() to read text
> files into lists... how can I do the same thing with dicts? Here's some
> sample output that I'd like to write to file and then read back into a dict:
>
> {'.\\sync_pics. py': 1135900993, '.\\file_histor y.txt': 1135900994,
> '.\\New Text Document.txt': 1135900552}
> --
> http://mail.python.org/mailman/listinfo/python-list
>[/color]

You can try the dict4ini module written by me.

http://wiki.woodpecker.org.cn/moin/Dict4Ini

The dict can be saved as an Ini file, and can be read back from the
Ini file.Just like:
[color=blue][color=green][color=darkred]
>>> import dict4ini
>>> x = {'.\\sync_pics. py': 1135900993, '.\\file_histor y.txt':[/color][/color][/color]
1135900994, '.\\New Text Document.txt': 1135900552}[color=blue][color=green][color=darkred]
>>> d = dict4ini.DictIn i(values=x)
>>> d['.\sync_pics.py '][/color][/color][/color]
1135900993

--
I like python!
My Blog: http://www.donews.net/limodou
NewEdit Maillist: http://groups.google.com/group/NewEdit

[Gary Herron]

Re: reading files into dicts

rbt wrote:
[color=blue]
>What's a good way to write a dictionary out to a file so that it can be
>easily read back into a dict later? I've used realines() to read text
>files into lists... how can I do the same thing with dicts? Here's some
>sample output that I'd like to write to file and then read back into a dict:
>
>{'.\\sync_pics .py': 1135900993, '.\\file_histor y.txt': 1135900994,
>'.\\New Text Document.txt': 1135900552}
>
>[/color]


A better way, than rolling your own marshaling (as this is called),
would be to use the cPickle module. It can write almost any Python
object to a file, and then read it back in later. It's more efficient,
and way more general than any code you're likely to write yourself.

The contents of the file are quite opaque to anything except the cPickle
and pickle modules. If you *do* want to roll you own input and output to
the file, the standard lib functions "repr" and "eval" can be used. Repr
is meant to write out objects so they can be read back in and recovered
with eval. If the contents of your dictionary are well behaved enough
(simple Python objects are, and classes you create may be made so), then
you may be able to get away with as little as this:

f = file('file.name ', 'wb')
f.write(repr(my Dictionary))
f.close()

and

f = file('file.name ', 'rb')
myDictionary = eval(f.read())
f.close()

Simple as that is, I'd still recommend the cPickle module.

As always, this security warning applys: Evaluating arbitrary text
allows anyone, who can change that text, to take over complete control
of your program. So be carefully.

Gary Herron

[Tim Williams (gmail)]

Re: reading files into dicts

A further thought, if you write the data to a file in the correct
format, you can use import and reload to access the data later instead
of repr.





On 12/29/05, Tim Williams (gmail) <tdwdotnet@gmai l.com> wrote:[color=blue]
> On 30/12/05, Giovanni Bajo <noway@sorry.co m> wrote:[color=green]
> >
> >[color=darkred]
> > >>> d = {'.\\sync_pics. py': 1135900993, '.\\file_histor y.txt':[/color][/color]
> 1135900994,[color=green]
> > .... '.\\New Text Document.txt': 1135900552}[color=darkred]
> > >>> file("foo", "w").write(repr (d))
> > >>> data = file("foo").rea d()
> > >>> data[/color]
> > "{'.\\\\sync_pi cs.py': 1135900993, '.\\\\file_hist ory.txt': 1135900994,
> > '.\\\\New Text Document.txt': 1135900552}"[color=darkred]
> > >>> d = eval(data)
> > >>> d[/color]
> > {'.\\sync_pics. py': 1135900993, '.\\file_histor y.txt': 1135900994,[/color]
> '.\\New[color=green]
> > Text
> > Document.txt': 1135900552}
> >
> > eval() is risky if you can't control the contents of the file :)[/color]
>
>[/color]


--

Tim Williams

[Tim Williams (gmail)]

Re: reading files into dicts

Apologies for the top post, it was my first attempt at using gmail's
pda-enabled web interface. There is no option to bottom post.

Apart from the mistake in my previous reply, when I meant to suggest
using import instead of eval() not repr(). I also omitted an example.
So here goes -but I don't know how gmail-CE will format this!!

Save your dict to a file with a .PY extension using

outdata = 'mydict =' + repr(dict) # or somesuch
similar

dictfile.py
-----------------------
mydict = {'key1':'a', 'key2':'b'}
-----------------------

Then:

import dictfile
print dictfile.mydict .keys()[color=blue][color=green][color=darkred]
>>>['key1','key2'][/color][/color][/color]
reload(dictfile )

HTH :-)

--

Tim Williams

[rbt]

Re: reading files into dicts

Gary Herron wrote:[color=blue]
> rbt wrote:
>[color=green]
>> What's a good way to write a dictionary out to a file so that it can
>> be easily read back into a dict later? I've used realines() to read
>> text files into lists... how can I do the same thing with dicts?
>> Here's some sample output that I'd like to write to file and then read
>> back into a dict:
>>
>> {'.\\sync_pics. py': 1135900993, '.\\file_histor y.txt': 1135900994,
>> '.\\New Text Document.txt': 1135900552}
>>
>>[/color]
>
>
> A better way, than rolling your own marshaling (as this is called),
> would be to use the cPickle module. It can write almost any Python
> object to a file, and then read it back in later. It's more efficient,
> and way more general than any code you're likely to write yourself.
>
> The contents of the file are quite opaque to anything except the cPickle
> and pickle modules. If you *do* want to roll you own input and output to
> the file, the standard lib functions "repr" and "eval" can be used. Repr
> is meant to write out objects so they can be read back in and recovered
> with eval. If the contents of your dictionary are well behaved enough
> (simple Python objects are, and classes you create may be made so), then
> you may be able to get away with as little as this:
>
> f = file('file.name ', 'wb')
> f.write(repr(my Dictionary))
> f.close()
>
> and
>
> f = file('file.name ', 'rb')
> myDictionary = eval(f.read())
> f.close()
>
> Simple as that is, I'd still recommend the cPickle module.
>
> As always, this security warning applys: Evaluating arbitrary text
> allows anyone, who can change that text, to take over complete control
> of your program. So be carefully.
>
> Gary Herron
>
>[/color]

Thanks to everyone for the tips on eval and repr. I went with the
cPickle suggestion... this is awesome! It was the easiest and quickest
solution performance-wise. Just makes me think, "Wow... how the heck
does pickle do that?!"

Thanks again,
rbt

[Chris F.A. Johnson]

Re: reading files into dicts

On 2005-12-30, Tim Williams (gmail) wrote:[color=blue]
> Apologies for the top post, it was my first attempt at using gmail's
> pda-enabled web interface. There is no option to bottom post.[/color]

Can you not move the cursor?

--
Chris F.A. Johnson, author | <http://cfaj.freeshell. org>
Shell Scripting Recipes: | My code in this post, if any,
A Problem-Solution Approach | is released under the
2005, Apress | GNU General Public Licence

[Fuzzyman]

Re: reading files into dicts

ConfigObj is good - it (effectively) turns a dictionary into an ini
file, and vice versa.

There is also built in support for type conversion.

See http://www.voidspace.org.uk/python/configobj.html

See the ConfigPersist module which has functions to use ConfigObj for
data persistence. It explains the limitations.

http://www.voidspace.org.uk/python/configpersist.html

Basically you can store and retrieve dictionaries, lists, strings,
integers, floats and booleans. You can nest dictionaries - but you
can't nest dictionaries in lists. All the keys must be strings - but
the module/article suggests a way round that, at the expense of
readability of the resulting text file.

All the best,

Fuzzyman
http://www.voidspace.org.uk/python/index.shtml

[Alex Martelli]

Re: reading files into dicts

rbt <rbt@athop1.ath .vt.edu> wrote:
...[color=blue]
> Thanks to everyone for the tips on eval and repr. I went with the
> cPickle suggestion... this is awesome! It was the easiest and quickest
> solution performance-wise. Just makes me think, "Wow... how the heck
> does pickle do that?!"[/color]

pickle.py implements just the same job, in pure Python, and it's easily
found within your Python's standard library, so you may want to study it
to see how it does perform its task.


Alex