functional programming python

sample.py

from itertools import takewhile, dropwhile
from functools import partial
#... some other imports

def some_table(context, series, format_string):
    table_options = format_string.split()

    is_same_date = lambda date, i: i.datestamp > date

    is_same_week = partial(is_same_date, context['date'] - timedelta(weeks=1))
    is_same_month = partial(is_same_date, context['date'] - timedelta(weeks=4))
    is_same_year = partial(is_same_date, context['date'] - timedelta(weeks=52))

    function_dict = {
        'd' : lambda series: series[0].price - series[1].price,
        'w' : lambda series: series[0].price - dropwhile(is_same_week, series).next().price,
        'm' : lambda series: series[0].price - dropwhile(is_same_month, series).next().price,
        'y' : lambda series: low_high(i.price for i in takewhile(is_same_year, series)),
    }

    table = []
    for series_name, series in series_set.items():
        try:
            row = dict([ (option, function_dict[option](series['list'])) for option in table_options ])
        except KeyError:
            raise template.TemplateSyntaxError("some_table has wrong arguments")
        except IndexError:
            raise template.TemplateSyntaxError("some_table : series does not contain enough data")
        row.update({
            'name' : series_name,
            'price' : series['list'][0].price,
        })
        table.append(row)

    return {
        'table': table,
    }