Kivy Date Picker Widget

Question

[SOLVED] Please see below for application of accepted answer and source code for functioning kivy DatePicker widget.

I've been learning Kivy and decided to make a date picker widgets as a learning exercise.

import kivy
kivy.require('1.4.0')    
from kivy.uix.gridlayout import GridLayout
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.uix.button import Button
from kivy.app import App

from datetime import date, timedelta

class DatePicker(BoxLayout):

    def __init__(self, **kwargs):
        super(DatePicker, self).__init__(**kwargs)
        self.date = date.today()
        self.orientation = "vertical"

        self.header = BoxLayout(orientation = 'horizontal', 
                                size_hint = (1, 0.2))
        self.body = GridLayout(cols = 7)
        self.add_widget(self.header)
        self.add_widget(self.body)

        self.populate_body()
        self.populate_header()

    def populate_header(self):
        self.header.clear_widgets()
        self.previous_month = Button(text = "<")
        self.next_month = Button(text = ">")
        self.current_month = Label(text = repr(self.date), 
                                   size_hint = (2, 1))

        self.header.add_widget(self.previous_month)
        self.header.add_widget(self.current_month)
        self.header.add_widget(self.next_month)

    def populate_body(self):
        self.body.clear_widgets()
        date_cursor = date(self.date.year, self.date.month, 1)
        while date_cursor.month == self.date.month:
            self.date_label = Label(text = str(date_cursor.day))
            self.body.add_widget(self.date_label)
            date_cursor += timedelta(days = 1)

# Not yet implimented ###
#    def set_date(self, day):
#        self.date = date(self.date.year, self.date.month, day)
#        self.populate_body()
#        self.populate_header()
#
#    def move_next_month(self):
#        if self.date.month == 12:
#            self.date = date(self.date.year + 1, 1, self.date.day)
#        else:
#            self.date = date(self.date.year, self.date.month + 1, self.date.day)
#    def move_previous_month(self):
#        if self.date.month == 1:
#            self.date = date(self.date.year - 1, 12, self.date.day)
#        else:
#            self.date = date(self.date.year, self.date.month -1, self.date.day)
#        self.populate_header()
#        self.populate_body()



class MyApp(App):

    def build(self):
        return DatePicker()

if __name__ == '__main__':
    MyApp().run()

I've hit a road block and can't work out how to continue. I want to add a method such that when the date_labels are clicked, they set self.date to a date object with that day part.

I've tried adding

self.date_label.bind(on_touch_down = self.set_date(date_cursor.day)) 

but only got max recursion errors.

SOLUTION:

import kivy

kivy.require('1.4.0')

from kivy.uix.gridlayout import GridLayout
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.label import Label
from kivy.uix.button import Button

from kivy.app import App

from datetime import date, timedelta

from functools import partial

class DatePicker(BoxLayout):

    def __init__(self, *args, **kwargs):
        super(DatePicker, self).__init__(**kwargs)
        self.date = date.today()
        self.orientation = "vertical"
        self.month_names = ('January',
                            'February', 
                            'March', 
                            'April', 
                            'May', 
                            'June', 
                            'July', 
                            'August', 
                            'September', 
                            'October',
                            'November',
                            'December')
        if kwargs.has_key("month_names"):
            self.month_names = kwargs['month_names']
        self.header = BoxLayout(orientation = 'horizontal', 
                                size_hint = (1, 0.2))
        self.body = GridLayout(cols = 7)
        self.add_widget(self.header)
        self.add_widget(self.body)

        self.populate_body()
        self.populate_header()

    def populate_header(self, *args, **kwargs):
        self.header.clear_widgets()
        previous_month = Button(text = "<")
        previous_month.bind(on_press=partial(self.move_previous_month))
        next_month = Button(text = ">", on_press = self.move_next_month)
        next_month.bind(on_press=partial(self.move_next_month))
        month_year_text = self.month_names[self.date.month -1] + ' ' + str(self.date.year)
        current_month = Label(text=month_year_text, size_hint = (2, 1))

        self.header.add_widget(previous_month)
        self.header.add_widget(current_month)
        self.header.add_widget(next_month)

    def populate_body(self, *args, **kwargs):
        self.body.clear_widgets()
        date_cursor = date(self.date.year, self.date.month, 1)
        for filler in range(date_cursor.isoweekday()-1):
            self.body.add_widget(Label(text=""))
        while date_cursor.month == self.date.month:
            date_label = Button(text = str(date_cursor.day))
            date_label.bind(on_press=partial(self.set_date, 
                                                  day=date_cursor.day))
            if self.date.day == date_cursor.day:
                date_label.background_normal, date_label.background_down = date_label.background_down, date_label.background_normal
            self.body.add_widget(date_label)
            date_cursor += timedelta(days = 1)

    def set_date(self, *args, **kwargs):
        self.date = date(self.date.year, self.date.month, kwargs['day'])
        self.populate_body()
        self.populate_header()

    def move_next_month(self, *args, **kwargs):
        if self.date.month == 12:
            self.date = date(self.date.year + 1, 1, self.date.day)
        else:
            self.date = date(self.date.year, self.date.month + 1, self.date.day)
        self.populate_header()
        self.populate_body()

    def move_previous_month(self, *args, **kwargs):
        if self.date.month == 1:
            self.date = date(self.date.year - 1, 12, self.date.day)
        else:
            self.date = date(self.date.year, self.date.month -1, self.date.day)
        self.populate_header()
        self.populate_body()



class MyApp(App):

    def build(self):
        return DatePicker()

if __name__ == '__main__':
    MyApp().run()

Answer 1

you do a small mistake in your binding, you call the method instead of passing it (thus, you pass the result of self.set_date(date_cursor.day), but calling self.set_date calls self.populate_body too, so you get in an infinite recursion, only stopped by python recursion limit.

What you want to do is bind the method but with date_cursor.day as a first parameter, for this the partial function, from functools is perfect.

self.date_label.bind(on_touch_down=partial(self.set_date, date_cursor.day))

Creates a new fonction, that is just like self.set_date, but with date_cursor.day preloaded as a first argument.

edit: also, when your partial function is called by the event binding, it will recieve other arguments, so it's a good habit to add **args at the end of your arguments in functions/methods you use ass callbacks (here set_date).