Build desktop applications with Python and Kivy

In recent years, the Python language has become more and more popular in the field of software development because of its characteristics such as easy to learn, easy to use, and easy to maintain. Kivy is a Python framework for building cross-platform user interfaces (UI) and is widely used to build mobile applications. However, desktop applications can also be built using Kivy, and this article will introduce how to build desktop applications using Python and Kivy.

1. Installing Python and Kivy

First you need to install Python and Kivy. The installation of Python is very simple, just download the version suitable for your operating system from the official website. After the installation is complete, open a command line window and enter the following command to install the Kivy framework:

pip install kivy

If you encounter installation problems, please check the official Kivy documentation for troubleshooting.

2. Create Kivy Application and Run

Next, we need to create a Kivy application and run it to make sure everything is working properly. In the IDE (Integrated Development Environment) of your choice (e.g. PyCharm), create a Python file and enter the following code:

import kivy
kivy.require('2.0.0')
from kivy.app import App
from kivy.uix.label import Label

class TestApp(App):
    def build(self):
        return Label(text='Hello, World!')

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

Briefly explain this code: First, import the Kivy library and required components, then Define an application class called TestApp. This class inherits from App and has a build method that returns an object with a Hello World text label. Finally, run the TestApp application class using the if __name__ == '__main__': statement.

Now, save this code as main.py or any other name and navigate to the directory containing this file in the command line window and run the following command:

python main.py

If everything Normally, you should see a label saying "Hello, World!" on the screen. Now that we have successfully created a Kivy application, we will focus on how to design a beautiful user interface.

3. Design Kivy user interface

In Kivy, the user interface is composed of widgets (Widgets), such as text labels, buttons, images, etc. Each widget has many properties and methods that can be used for styling, formatting, responding to user input and interaction, and more.

The following is a simple example showing how to use Kivy's GridLayout layout and add three different types of widgets: two labels and a button.

import kivy
kivy.require('2.0.0')

from kivy.app import App
from kivy.uix.button import Button
from kivy.uix.label import Label
from kivy.uix.gridlayout import GridLayout

class MyGridLayout(GridLayout):
    def __init__(self, **kwargs):
        super(MyGridLayout, self).__init__(**kwargs)
        self.cols = 1 # 将列数设置为1

        # 添加第一个标签
        self.add_widget(Label(text="Name:"))

        # 添加第一个输入框
        self.name = TextInput(multiline=False)
        self.add_widget(self.name)

        # 添加第二个标签
        self.add_widget(Label(text="Favorite Color:"))

        # 添加第二个输入框
        self.color = TextInput(multiline=False)
        self.add_widget(self.color)

        # 添加按钮
        self.submit = Button(text="Submit", font_size=16)
        self.submit.bind(on_press=self.press)
        self.add_widget(self.submit)

    def press(self, instance):
        name = self.name.text
        color = self.color.text

        # 将文本清空
        self.name.text = ""
        self.color.text = ""

        print(f'Hello, {name}, you like {color}!')

class MyApp(App):
    def build(self):
        return MyGridLayout()

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

This code uses GridLayout layout to arrange all the widgets into separate columns. In the constructor, we added two labels and two text input boxes and printed out the input text when the "Submit" button was clicked.

Now that we understand how to use Kivy to create beautiful user interfaces, let's briefly introduce how to integrate Python code.

4. Integrating Python code

So far we have been able to use Python and Kivy to create a user interface, but if you need to integrate other Python code into the application, it Requires some extra work.

Consider the following situation: you need to use the Pandas library to load and process data in your application. First, enter the following command on the command line to install Pandas:

pip install pandas

Then, open the main.py file and import the numpy and pandas libraries at the beginning of the file, for example:

import numpy as np
import pandas as pd

In MyGridLayout Add a new method load_data, which uses the pandas library to load data and add it to the GridLayout. For example:

def load_data(self, filename):
    df = pd.read_csv(filename)

    for index, row in df.iterrows():
        # 添加文本标签来显示数据
        self.add_widget(Label(text=row['name']))
        self.add_widget(Label(text=row['color']))
        self.add_widget(Label(text=row['fruit']))

Now you can use this method in the application to load the data file and display it as Kivy's user interface.

To sum up, this article introduces how to use Python and Kivy to build desktop applications, including installing Python and Kivy, creating Kivy applications and designing Kivy user interfaces. Additionally, how to integrate Python code is explained. I hope this article is helpful to readers who want to build desktop applications using Kivy.

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