[Tutor] counting a list of elements

[Karim]

On 04/01/2011 08:41 PM, Knacktus wrote:
> Am 01.04.2011 19:16, schrieb Karim:
>>
>>
>> Hello,
>>
>> I would like to get advice on the best practice to count elements in a
>> list (built from scractch).
>> The number of elements is in the range 1e3 and 1e6.
>>
>> 1) I could create a generator and set a counter (i +=1) in the loop.
>>
>> 2) or simply len(mylist).
>>
>> I don't need the content of the list, indeed, in term of memory I don't
>> want to wast it. But I suppose len() is optimized too (C impementation).
>>
>> If you have some thought to share don't hesitate.
>
> Just a general suggestion: Provide code examples. I know most of the 
> times you don't have code examples yet as you're thinking of how to 
> solve your problems. But if you post one of the possible solutions the 
> experienced guys here will very likely direct you in the proper 
> direction. But without code it's hard to understand what you're after.
>
> Cheers,
>
> Jan
>

Thank you all for you answers to clarified I built a collection of 
dictionnaries which represent database query on a bug tracking system:

backlog_tables ,   csv_backlog_table   = _backlog_database(table=table, 
periods=intervals_list)

backlog_tables is a dictionnary of bug info dictionnaries. The keys of 
backlog_tables is a time intervall (YEAR-MONTH) as shown below:

backlog_tables= {'2011-01-01': [{'Assigned Date': datetime.date(2010, 
10, 25),
                  'Category': 'Customer_claim',
                  'Date': datetime.date(2010, 10, 22),
                  'Duplicate Date': None,
                  'Fixed Reference': None,
                  'Headline': 'Impovement for all test',
                  'Identifier': '23269',
                  'Last Modified': datetime.date(2010, 10, 25),
                  'Priority': 'Low',
                  'Project': 'MY_PROJECT',
                  'Reference': 'MY_PROJECT at 1.7beta2@20101006.0',
                  'Resolved Date': None,
                  'Severity': 'improvement',
                  'State': 'A',
                  'Submitter': 'Somebody'},
                  .....
                  }

_backlog_database() compute the tuple backlog_tables ,   csv_backlog_table:
In fact csv_backlog_table is the same as backlog_tables but instead of 
having
the query dictionnaries it holds only the number of query which I use to 
create
a CSV file and a graph over time range.

_backlog_database() is as follow:

def _backlog_database(table=None, periods=None):
     """Internal function. Re-arrange database table
     according to a time period. Only monthly management
     is computed in this version.

     @param  table   the database of the list of defects. Each defect is 
a dictionnary with fixed keys.
     @param  periods the intervals list of months and the first element 
is the starting date and the
                     the last element is the ending date in string format.
     @return (periods_tables, csv_table),  a tuple of periodic 
dictionnary table and
             the same keys dictionnary with defect numbers associated 
values.
     """
     if periods is None:
         raise ValueError('Time interval could not be empty!')

     periods_tables = {}
     csv_table      = {}

     interval_table = []

     for interval in periods:
         split_date = interval.split('-')
         for row in table:
             if not len(split_date) == 3:
                 limit_date = 
_first_next_month_day(year=int(split_date[0]), month=int(split_date[1]), 
day=1)
                 if row['Date'] < limit_date:
                    if not row['Resolved Date']:
                        if row['State'] == 'K':
                            if row['Last Modified'] >= limit_date:
                                interval_table.append(row)
                        elif row['State'] == 'D':
                            if row['Duplicate Date'] >= limit_date:
                                interval_table.append(row)
                        # New, Assigned, Opened, Postponed, Forwarded, 
cases.
                        else:
                            interval_table.append(row)
                   else:
                        if row['Resolved Date'] >= limit_date:
                            interval_table.append(row)

         periods_tables[interval] = interval_table
         csv_table[interval]      = str(len(interval_table))

         interval_table = []

     return periods_tables, csv_table


This is not the whole function I reduce it on normal case but it shows 
what I am doing.
In fact I choose to have both dictionnaries to debug my function and 
analyse what's going
on. When everything will be fine I will need only the csv table (with 
number per period) to create the graphs.
That's why I was asking for length computing. Honnestly, the actual 
queries number is 500 (bug id) but It could be more
in other project. I was ambitious when I sais 1000 to 100000 
dictionnaries elements but for the whole
list of products we have internally It could be 50000.

Regards
Karim

>
>>
>> Karim
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