Building GUI application using Python

Hi Guys!

Today, We’ll be exploring to create a GUI application using Python.

We’ll be using a briefcase package, one of the popular utilities from Python-verse.

The advantage of this package is you can create an application on Windows, MAC, Linux & Android using the same piece of code.

Let’s explore!

Step – 1:

We’ll be installing briefcase package –

1. Installing Packages - 1

Step – 2:

Install the toga package –

2. Installing Packages - 2.JPG

Step – 3:

Install the pycairo package –

3. Installing Packages - 3

Some O/S, you might not be able to install pycairo. In that case, you need to install it from a third-party site & need to install a wheel package.

4. Installing Packages - 4

Step – 4:

Finally, the last package –

5. Installing Packages - 5
  • For Windows, you need to install the Wix toolset.
  • For MAC, there is no additional tool you need to install.
  • For iOS, You need to have X-Code & a developer account.
  • For Linux, You need to install GTK 3.10 or later.
  • For Android, you need to install the Android studio.
  • For web-app, you need to use the Django framework.

Let’s create the virtual directory –

python -m venv –copies .env

.env\Scripts\activate.bat

Let’s create the default app –

There will be a series of inputs that you need to pass it to create the default application –

6. Creating First Step

Please find the RED highlighted options.

Let’s find the run commands for different environments  –

python setup.py windows -s

python setup.py macos -s

python setup.py linux -s

python setup.py ios -s

python setup.py android -s

Let’s run that in Windows –

7. Creating First App

Now, we’ll modify our code & we’ll add some text field & calculation logic in this Apps.

Let’s review the central directory structure –

11. Main Directory Structures

Now, explore the SDPythonApp directory & we’ll find the following structure –

10. Directory Structure

Let’s discuss our code –

1. app.py (This script will contain the main logic of GUI Apps & will invoke be the main application)

###############################################
#### Written By: SATYAKI DE                ####
#### Written On: 24-Nov-2019               ####
####                                       ####
#### Objective: This script will create a  ####
#### GUI application with sample function. ####
####                                       ####
###############################################

"""
First IOS App made from Python
"""
import toga
from toga.style import Pack
from toga.style.pack import COLUMN, ROW, LEFT, RIGHT


class Sdapp(toga.App):

    def two_digit_decimal(self, n1):
        n = round(n1, 2)
        return n

    def calculate(self, widget):
        try:
            # Dummy Tax Calculation
            val = (float(self.f_input.value) * 4.5) * 2.7 / 100.0
            self.c_input.value = self.two_digit_decimal(val)
        except Exception:
            self.c_input.value = 'Please provide numeric values!'

    def startup(self):
        # Create a main window with a name matching the app
        self.main_window = toga.MainWindow(title=self.name)

        # Create a main content box
        f_box = toga.Box()
        c_box = toga.Box()
        box = toga.Box()

        self.c_input = toga.TextInput(readonly=True)
        self.f_input = toga.TextInput()

        self.c_label = toga.Label('$', style=Pack(text_align=LEFT))
        self.f_label = toga.Label('Salary', style=Pack(text_align=LEFT))
        self.join_label = toga.Label('Tax Amount', style=Pack(text_align=RIGHT))

        # Button Activity
        button = toga.Button('Generate Tax', on_press=self.calculate)

        f_box.add(self.f_input)
        f_box.add(self.f_label)

        c_box.add(self.join_label)
        c_box.add(self.c_input)
        c_box.add(self.c_label)

        box.add(f_box)
        box.add(c_box)
        box.add(button)

        box.style.update(direction=COLUMN, padding_top=10)
        f_box.style.update(direction=ROW, padding=5)
        c_box.style.update(direction=ROW, padding=5)

        self.c_input.style.update(flex=1)
        self.f_input.style.update(flex=1, padding_left=160)
        self.c_label.style.update(width=100, padding_left=10)
        self.f_label.style.update(width=100, padding_left=10)
        self.join_label.style.update(width=150, padding_right=10)

        button.style.update(padding=15, flex=1)

        # Add the content on the main window
        self.main_window.content = box

        # Show the main window
        self.main_window.show()


def main():
    return Sdapp('SDApp', 'com.firstapp.SDPythonApp')

Let’s discuss the key lines –

self.c_label = toga.Label('

The following lines are textbox boilerplate in the main application.

# Button Activity
button = toga.Button('Generate Tax', on_press=self.calculate)

The above lines will trigger the event when someone clicks the application & it will trigger the function named calculate.

def calculate(self, widget):
    try:
        # Dummy Tax Calculation
        val = (float(self.f_input.value) * 4.5) * 2.7 / 100.0
        self.c_input.value = self.two_digit_decimal(val)
    except Exception:
        self.c_input.value = 'Please provide numeric values!'

In the above function, we’ve prepared a dummy calculation logic for TAX calculation. And, finally, we’ll be extracting two digits numeric digits after decimal by invoking the two_digit_decimal function.

def two_digit_decimal(self, n1):
    n = round(n1, 2)
    return n

This function will return two digits after decimal places.

In the above function, we’ve prepared a dummy calculation logic for TAX calculation. And, finally, we’ll be extracting two digits numeric digits after decimal by invoking the two_digit_decimal function.

Let’s run our application –

8.1. Before Advanced App

Let’s provide input say 1234 as shown in the above figures & click the Generate Tax button marked in RED. This will prompt the following screen.

8. Advanced App

Let’s explore if someone provides invalid input –

9. Exception Cases

As expected, this will throw a proper warning to its application user.

So, we’ve done it. Building our first python based GUI application across multiple platforms.

Please share your review.

So, we’ll come out with another new post in the coming days!

N.B.: This is demonstrated for RnD/study purposes. All the data posted here are representational data & available over the internet & for educational purpose only.

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