flexible date like '+2 days' 'friday' '+2 thursday'

flexible_date.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
#       Copyright 2011 mishudark <moonsadly@gmail.com><mishudark@astrata.com.mx>
#       
#       This program is free software; you can redistribute it and/or modify
#       it under the terms of the GNU General Public License as published by
#       the Free Software Foundation; either version 2 of the License, or
#       (at your option) any later version.
#       
#       This program is distributed in the hope that it will be useful,
#       but WITHOUT ANY WARRANTY; without even the implied warranty of
#       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#       GNU General Public License for more details.
#       
#       You should have received a copy of the GNU General Public License
#       along with this program; if not, write to the Free Software
#       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
#       MA 02110-1301, USA.
#

import re
import datetime
"""
usage:
  #some posible values
  value = '+1 days'
  value = '+5 months'
  value = '+1 wednesday'
  value = '+2 friday'
  value = 'monday'
  
  flexible_date(value)
  #return a date format d-m-Y
"""

def flexible_date(value):
    options = {
            'month':'m', 'mes':'m',
            'months':'m', 'meses':'m',
            'year':'y', 'año':'y',
            'years':'y', 'años':'y',
            'day':'d', 'dia':'d',
            'days':'d', 'dias':'d',
            }
    days = {
            'monday':1, 'lunes':1,
            'tuesday':2, 'martes':2,
            'wednesday':3, 'miercoles':3,
            'thursday':4, 'jueves':4,
            'friday':5, 'viernes':5,
            'saturday':6, 'sabado':6,
            'sunday':7, 'domingo':7,
            }
    logical = {
            'now':0, 'ahora':0,
            'today':0, 'hoy':0,
            'tomorrow':1, 'mañana':1,
            }

    value = value.replace('/','-')
    
    #Regex
    normal = '([0-9]{1,2}\-[0-9]{1,2}\-[0-9]{0,4})'
    relative = '([\+\-]?[0-9]+\s\w+)'

    date = re.findall(normal,value)
    if(len(date)>0):
        return date[0]

    #find format like '+1 days'
    date = re.findall(relative,value)
    if(len(date)>0):
        value = date[0]
        [num,item] = value.split(' ')
        num = int(num)
    else:
        item = value;
        num = 1;
    
    #get diference between now an relative date
    today = datetime.date.today()
    if item in days:
        num += 1
        if (num * 7 - 7 + days[item]) > today.weekday():
            diff = num * 7 - 7 + days[item] - today.weekday() -1
        else:
            diff = num * 7 + days[item] - today.weekday() -1
        #correct date
        correct = today + datetime.timedelta(days = diff)

        d = correct.day
        m = correct.month
        y = correct.year
        date = "%d-%d-%d" % (d,m,y)

    elif item in logical:    
        diff = logical[item]
        #correct date
        correct = today + datetime.timedelta(days = diff)

        d = correct.day
        m = correct.month
        y = correct.year
        date = "%d-%d-%d" % (d,m,y)

    elif item in options:
        d = today.day
        m = today.month
        y = today.year

        if options[item] == 'm':
            m = (m + num) % 12
            y += int( (m + num -1) / 12 )
        elif options[item] == 'y':
            y += num
        elif options[item] == 'd':
            today += datetime.timedelta(days = num)
            d = today.day
            m = today.month
            y = today.year

        date = "%d-%d-%d" % (d,m,y)

    else:
        date = ''
        
    return date