如何使用Python和kivy输入条件语句？

Question

I'm new to kivy. I was writing the following code using python and kivy which is a quite simple one that asks the user for his/her name and hunger level.

import kivy #import kivy module
kivy.require('1.0.6') # replace with your current kivy version !

from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.gridlayout import GridLayout  
from kivy.uix.textinput import TextInput  

class human(GridLayout):
    #This is a human class
    def __init__(self, **kwargs):
        super(human, self).__init__(**kwargs)
        self.cols = 2 
        self.add_widget(Label(text='Enter your name')) 
        self.name = TextInput(multiline=False) 
        self.add_widget(self.name)
        self.add_widget(Label(text='Enter your hunger level(0-10)'))
        self.hunger = TextInput(multiline=False)
        self.add_widget(self.hunger)

class MyApp(App):

    def build(self):
        return human()


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

Now I would like to have a conditional statement that will check whether the hunger level entered is less than 5 or not. If so, it will print "normal" else it will print "abnormal".

What should I do?

Answer 1

You obviously can't check for the hunger level immediatly, before the end of the build() method, the user probably didn't even see a window yet, so you have to organise the code for it to check the value after some time, the question is when , usually, you want to react to some event, rather than wait a specific amount of time. Kivy offers ways to do either.

You could decide that the user has to validate its input by pressing a button. To do that, you would add. self.add_widget(Button(text="ok", on_press=self.check_hunger)

and add a check_hunger method to human , which would check the current text in self.hunger.

But you could decide to be more reactive, and instead to react to any validation of the textinput. To achieve this instead, you can just bind check_hunger to the on_text_validate event of hunger.

add self.hunger.bind(on_text_validate=self.hunger) after self.hunger = TextInput(multiline=False)

or simply edit this line to read self.hunger = TextInput(multiline=False, on_text_validate=self.check_hunger)

and just for the sake of the example, if you wanted to check the hunger after some definite time instead, you could add at the top of your program: from kivy.clock import Clock and put Clock.schedule_once(self.check_hunger, 5) at the end of your __init__ method.

Anyway, to achieve what you asked for, the check_hunger method would look something like:

def check_hunger(self, *args): if int(self.hunger.text) < 5: print("normal") else: print("abnormal")

hope it helps!

Answer 2

After you've instantiated your human class you can access to hunger level by just writing human_instance.hunger .

You can try the below code:

import kivy #import kivy module
kivy.require('1.0.6') # replace with your current kivy version !

from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.gridlayout import GridLayout  
from kivy.uix.textinput import TextInput  

class human(GridLayout):
    #This is a human class
    def __init__(self, **kwargs):
        super(human, self).__init__(**kwargs)
        self.cols = 2 
        self.add_widget(Label(text='Enter your name')) 
        self.name = TextInput(multiline=False) 
        self.add_widget(self.name)
        self.add_widget(Label(text='Enter your hunger level(0-10)'))
        self.hunger = TextInput(multiline=False)
        self.add_widget(self.hunger)

class MyApp(App):

    def build(self):
        return human()


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

    my_human = my_app.build()

    if my_human.hunger < 5:
        print('Normal')
    else:
        print('Abnormal')

I'm not sure if this code will run or not because I don't know if kivy's app's run method is blocking or non-blocking. But you can understand the logic from this code.