How to make tree of dictionaries?

Aahz aahz at pythoncraft.com
Wed Aug 13 04:55:45 CEST 2003


In article <87fzk6tuoq.fsf at big.terem>, Vlad Sirenko  <zcoder at bigmir.net> wrote:
>I need:
>dict = {2002 : {'Jan': {1 : 'num1', 2: 'num2', 3 : 'num3'}, 
>               {'Feb': {1 : 'num4', 2: 'num5', 3 : 'num6'} } }
>        2003 : {'Jan': {1 : 'num7', 2: 'num8', 3 : 'num9'} } }
>
>How to do it programmatically?
>In Perl I would do something like:
>
>while ($line = <>) {
>  if ($line =~ /^---\s+\w+\s+(\w+)\s+(\d*)\s+(\d+):(\d+):(\d+)\s+(\d+)\s+---$/) {
>	($month,$date,$hour,$minute,$sec,$year) = ($1,$2,$3,$4,$5,$6);
>	$statistics->{$year}->{$month}->{$date} += $sec;
>  }
>}
>
>But how to do it in Python without catching 'KeyError' exception or
>iterating over some nested loops. How to do it elegantly?

You don't need nested loops, but you do need multiple statements:

    tmp_year = stats.setdefault(year, {})
    tmp_month = tmp_year.setdefault(month, {})
    tmp_month[date] = tmp_month.setdefault(date, 0) + sec
-- 
Aahz (aahz at pythoncraft.com)           <*>         http://www.pythoncraft.com/

This is Python.  We don't care much about theory, except where it intersects 
with useful practice.  --Aahz




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