reading files into dicts

[rbt]

Gary Herron wrote:
> rbt wrote:
> 
>> 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_history.txt': 1135900994, 
>> '.\\New Text Document.txt': 1135900552}
>>  
>>
> 
> 
> 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(myDictionary))
> 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
> 
> 

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