newbie: datastructure `dictionary' question

Diez B. Roggisch deets at nospam.web.de
Sat Sep 9 17:52:30 CEST 2006


jason schrieb:
> Hello,
> 
> I am completely new to python and I have question that I unfortunately
> could not find in the various documentation online. My best guess is
> that the answer should be quitte easy but I have just enterd the learning
> phase so that means a hightend chance for stupidity and mistakes on my
> part.
> 
> I am trying to fill a nested dictionary from parsing a logfile. However
> each time there is only one key entry created and that's it. Just
> one entry, while the keys are different. That's 100% sure. I think
> therefore that it is an assignment error in my part. [there we have it...]
> 
> To give an static example of the datastructure that I am using to clear
> any confusion on the datastructure part:
> 
>     records = { 'fam/jason-a' : {
>         'date'    : 'Fri Sep  8 16:45:55 2006',
>         'from'    : 'jason',
>         'subject' : 'Re: Oh my goes.....',
>         'msize'   : '237284' },
>                 'university/solar-system' : {
>         'date'    : 'Fri Sep  8 16:45:46 2006',
>         'from'    : 'jd',
>         'subject' : 'Vacancies for students',
>         'msize'   : '9387' }
>     }
> 
> Looping over this datastructure is no problem.
>     rkeys = ['date', 'from', 'subject', 'msize']
>     for folder in records.keys():
>         print '--'
>         print folder
>         for key in rkeys:
>             print records[folder][key]
> 
> Now for the actual program/dynamic part - assignment in the loop I use the
> following function. Note `datum' is not a date object, just a string.
> 
> def parselog(data):
>     other = 0
>     records = {}
> 
>     for line in string.split(data, '\n'):
>         str = line.strip()
>         if str[:4] == 'From':
>             mfrom, datum = extrfrom(str), extrdate(str)
>             print datum, mfrom
>         elif str[:4] == 'Fold':
>             folder = extrfolder(str[8:])
>             records = {folder : { 'date' : datum, 'mesgbytes' : extrmsize(str[8:]), 'mesgcount' : 1}}
>         else:
>             other += 1
> 
>     displrec(records)
> 
> Note, this is not ment as a collision type datastructure, all initial data
> entries are unique. My question: Where is my assignment e.g. records =
> {folder.... wrong ?

What you essentially do is this:

records = {"some" : "dict"}
records = {"some other" : "dict"}

You rebind the name records to a new dictionary. So all your previously 
stored data is garbage collected.

What you most probably want to do (I'm a bit confused about your code & 
too lazy to dig deeper):

records = {}

records[folder] = {'date' : ...}

Notice that the dict[key]=value syntax mutates the existing dictionary.

Diez



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