Lesson 8: APIs and Building GUI with Tkinter

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Lesson 8: APIs and Building GUI with Tkinter#

Owner: (sx Shirsat, Rushikesh)

  • Prerequisite topics:

    • Hyatt, Matt

    • suggestion only

  • Hyatt, Matt other suggestion:

Suggested Chapter Title -> Building GUI Apps with Tkinter and APIs in Python

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We have separated this chapter into two parts Part 1 is Understanding API’s & Part 2 is Building GUI with Tkinter

INDEX

Part 1: Understanding APIs#

1. Introduction to APIs#

  • What is an API (Application Programming Interface)?

  • Why APIs are used (communication between software applications)

  • Examples of real-world APIs (weather data, currency converter, YouTube, etc.)

2. Types of APIs#

  • Web APIs (REST, SOAP)

  • Local APIs / Library APIs

  • Public vs. Private APIs

3. How Web APIs Work#

  • Client-Server model

  • Endpoints and HTTP methods (GET , POST , PUT , DELETE)

  • Understanding JSON (JavaScript Object Notation) format

  • Example of an API request and response

4. Using APIs in Python#

  • Installing and importing requests module

  • Sending a GET request

  • Parsing JSON response

  • Handling errors and exceptions

5. Example Projects#

  • Fetching data from a public API (e.g., OpenWeatherMap, Cat Facts API, etc.)

  • Displaying API data in the terminal

Part 2: Building GUIs with Tkinter#

6. Introduction to Tkinter#

  • What is Tkinter?

  • Setting up the environment

  • Basic structure of a Tkinter program

  • Creating the main window ( Tk() )

7. Widgets in Tkinter#

  • Labels, Buttons, Entry, Text, Frame, Canvas, Listbox

  • Widget options (text, font, color, etc.)

  • Geometry managers ( pack, grid, place )

8. Handling Events#

  • Button click events ( command parameter)

  • Getting user input from Entry

  • Updating label text dynamically

9. Layout and Styling#

  • Frames and organizing the window

  • Using padding, alignment, and resizing

  • Introduction to ttk for modern-looking widgets

10. Integrating APIs with Tkinter GUI#

  • Combining Tkinter with an API call

  • Displaying live data (like weather info) in a GUI

  • Handling user input (e.g., user enters a city name → app fetches data via API)

11. Example Mini Projects#

  • Weather App using OpenWeatherMap API

  • Random Cat Facts App

  • Currency Converter App

  • Movie Search App using OMDb API

12. Error Handling and Debugging#

  • Handling invalid user inputs

  • Managing failed API requests (timeouts, invalid keys, etc.)

  • Showing error messages in GUI ( messagebox )

13. Packaging and Running#

  • Running your GUI application

  • Converting your Python GUI to an executable (.exe) using pyinstaller

Lesson : APIs and Tkinter Set Started

Introduction

In modern programming, applications rarely work in isolation. They often need to interact with other programs, services, or users. Two important concepts that help us build powerful and interactive applications are APIs and Graphical User Interfaces (GUIs).

  • APIs allow your program to communicate with other software, services, or data providers over the internet.

  • Tkinter lets you create graphical interfaces, so your program is easier to use and more interactive.

1. Introduction to APIs#

What is an API?#

  • API (Application Programming Interface) is a set of rules that allows one piece of software to interact with another.

  • Think of it as a bridge between two systems that lets them share data and functionality.

Real-Life Analogy#

Imagine a restaurant:

  • You (the user) → make a request.

  • Waiter (the API) → takes your order to the kitchen.

  • Kitchen (the server) → prepares the food (data) and gives it back to you via the waiter.

Similarly, in programming:

  • The client sends a request.

  • The server processes it and sends a response.

Request
Client Response

API
Server

Why APIs Are Important#

  • They enable data sharing between apps (e.g., Google Maps integrated in ride-sharing apps).

  • Help developers build feature-rich apps faster without reinventing the wheel.

  • Provide access to third-party services like weather info, social media, news, etc.

Common Examples#

  • Weather Apps – use APIs like OpenWeatherMap

  • Currency Converters – use ExchangeRate API

1.1 Types of APIs#

1. Web APIs#

2. Library or Local APIs#

  • Built into programming languages or libraries.

  • Example: Python’s math module ( math.sqrt() ) is an API that lets you use mathematical functions.

3. Public vs. Private APIs#

Type

Description

Example

Public API

Open to everyone, usually free or with a key

OpenWeatherMap

Private API

Restricted for internal use within an organization

Google’s internal APIs

Partner API

Shared between companies under agreements

PayPal merchant APIs

1.3. How Web APIs Work#

Client-Server Model#

  1. Client (your app) sends a request.

  2. Server processes it.

  3. Server sends back a response (usually in JSON).

API Request and Response Example#

Request URL:

Response (JSON):

HTTP Methods#

Method

Purpose

Example

GET

Retrieve data

Get weather data

POST

Send new data

Submit a form

PUT

Update existing data

Edit a profile

DELETE

Remove data

Delete a note

Endpoints#

  • Each URL path is an endpoint (specific resource on the server).

Example:

https://api.github.com/users/octocat/repos → endpoint for user repositories.

Using APIs in Python#

To use APIs, we often use the requests library.

Step 1: Install and Import#

pip install requests

import requests

Step 2: Send a GET Request#

response = requests.get("https://api.github.com/users/octocat")

Step 3: Check Status#

print(response.status_code)  # 200 means success

Step 4: Parse JSON Data#

data = response.json()
print(data["name"])

Output Example:

The Octocat

Step 5: Handle Errors#

if response.status_code != 200:
    print("Error:", response.status_code)
else:
    print(data["name"])

5. Example Projects (for Practice)#

Example 1: Simple Weather Fetcher#

Example 2: Random Cat Fact#

Example 3: Currency Converter#

TIPS#

  • APIs let your app communicate with other systems.

  • Use the requests module for HTTP operations.

  • JSON is the most common data format for APIs.

  • Always handle errors and check status_code.

  • Practice with public APIs before working with private ones.

Example: Getting Weather Data#

Imagine you want to build a program that shows the current temperature in a city. Instead of collecting and updating weather data yourself, you can use a weather API like OpenWeatherMap.

Step-by-step: Using OpenWeatherMap API in Python#

  1. Sign up at OpenWeatherMap https://openweathermap.org/

  2. Understand the API endpoint (URL) you need to call: https://api.openweathermap.org/data/2.5/weather?q=city_name&appid=API_key&units=metric

  3. Write Python code to send a request and process the response.

What are we doing in the code#

  • We used the requests.get() method to send an HTTP GET request to the API.

  • We passed parameters (city, api_key, units) to the API.

  • We checked if the request was successful (status_code == 200).

  • We converted the JSON response into a Python dictionary using.json().

  • We extracted and printed useful information: temperature and weather description.

Part A: Multiple-Choice Questions (MCQs)#

Choose the correct answer

  1. What does API stand for?

  1. Application Programming Interface

  2. Advanced Program Integration

  3. Automated Process Input

  4. Applied Programming Interaction

  1. Which of the following is NOT a common HTTP method used in APIs?

  1. GET

  2. POST

  3. FETCH

  4. DELETE

  1. What is the purpose of an API key?

  1. To encrypt JSON data

  2. To identify and authenticate the user or app making a request

  3. To make the response faster

  4. To store client data

  1. Which of the following Python libraries is commonly used to work with APIs?

  1. os

  2. math

  3. requests

  4. pandas

  1. What is the most common data format used in API responses?

  1. XML

  2. HTML

  3. JSON

  4. CSV

  1. In the URL [https://api.github.com/users/octocat, what is the endpoint?]

  1. https://api.github.com

  2. /users/octocat

  3. octocat

  4. api.github.com

  1. What does the status code ``404`` represent?

  1. Success

  2. Server error

  3. Not found

  4. Bad request

  1. Which function from the ``requests`` library retrieves the JSON data?

  1. response.text()

  2. response.html()

  3. response.json()

  4. response.data()

  1. If ``response.status_code == 200``, what does that mean?

  1. Request failed

  2. Request succeeded

  3. Server busy

  4. Unauthorized access

10 What will happen if you call an API without an internet connection?

  1. Returns empty JSON

  2. Raises a requests.exceptions.ConnectionError

  3. Returns 404

  4. Prints nothing

☑ Answer Key (for instructors/self-check):

1-a, 2-c, 3-b, 4-c, 5-c, 6-b, 7-c, 8-c, 9-b, 10-b

Short Answer Questions#

Write short answers (2–3 sentences each):

  1. Explain what an API is and give one real-world example.

  2. Differentiate between public and private APIs.

  3. What is JSON, and why is it preferred in APIs?

  4. What does the requests.get() function do in Python?

  5. What is the role of endpoints in an API?

  6. What happens when an invalid city name is sent to a weather API?

  7. How can you handle API errors in Python?

  8. What is the difference between GET and POST requests?

Part C: Coding Exercises#

Exercise 1: Get a Joke from an API#

Task:

Write a Python program that fetches and prints a random joke using this API:

url = "https://official-joke-api.appspot.com/random_joke"

Hint:

The JSON response looks like:

{
  "setup": "Why did the chicken cross the road?",
  "punchline": "To get to the other side!"
}

Expected Output:

Why did the chicken cross the road?
To get to the other side!

Exercise 2: Cat Facts API#

Task:

Use the API [https://catfact.ninja/fact] to display a random cat fact.

If the request fails, print [“Error fetching data.”]

Exercise 3: Weather Data (Mini Project)#

Task:

Ask the user for a city name and display the temperature and condition using:

url = f"http://api.openweathermap.org/data/2.5/weather?q={city}&appid=YOUR_API_KEY&units=metric"

(This API doesn’t require a key)

Example Output:

Enter city name: London
Temperature: 15°C, Condition: cloudy

Exercise 4: Explore JSON Keys#

Task:

Fetch data from

url = "https://api.github.com/users/octocat"

and print only the following:

  • login

  • public_repos

  • followers

Exercise 5: Error Handling Practice#

Task:

Write a Python script that requests data from an invalid API endpoint.

Use a [try-except] block to handle the RequestException and print [“Network error or invalid URL.”]

Introduction to GUI (Graphical User Interface)#

A Graphical User Interface (GUI) is a type of user interface that allows people to interact with a computer using visual elements such as windows, buttons, text boxes, icons, sliders, dropdowns, and images.

Unlike command-line programs where users must type instructions, a GUI lets users perform actions using the mouse, keyboard, or touch, making applications more user-friendly, intuitive, and accessible to beginners.

Why Do We Use GUIs?#

  • They are easier to use than typing commands.

  • They provide visual feedback, so users immediately see results.

  • They make software look modern and professional.

  • They allow users to interact without knowing programming commands.

  • They minimize user mistakes through menus, buttons, and prompts.

Real-World Examples of GUIs#

You interact with GUIs every day: - Windows and macOS desktops - Mobile apps - Calculator apps - File Explorer / Finder - Web browsers like Chrome and Firefox - Video players, drawing tools, games, dashboards, etc.

Every app with buttons, colors, menus, or pop-ups is a GUI application.

6. What is Tkinter?#

  • Tkinter is Python’s built-in library for creating Graphical User Interfaces (GUIs).

  • It allows you to build desktop applications with buttons, text boxes, menus, and more.

  • It comes pre-installed with Python, so no extra installation is needed.

How Tkinter Works#

  • Tkinter acts as a bridge between Python and the Tcl/Tk GUI toolkit.

  • The main window of the application is created using the Tk() object.

Structure of a Simple Tkinter Program#

import tkinter as tk

root = tk.Tk()
root.title("My First GUI")

label = tk.Label(root, text="Hello, Tkinter!")
label.pack()

root.mainloop()

Explanation 1. tk.Tk() → Creates the main window. 2. Label → A widget that displays text. 3. pack() → Places the widget in the window. 4. mainloop() → Keeps the window open and listens for user actions.

7. Tkinter Widgets#

Widgets are the building blocks of a GUI.

Commonly Used Widgets#

Widget

Purpose

Label

Display text or images

Button

Perform an action when clicked

Entry

Accept single-line text input

Text

Multi-line text input

Frame

Container for grouping widgets

Listbox

Display a list of items

Canvas

Draw shapes or graphics

Checkbutton

Create checkboxes

Example: Label and Button#

import tkinter as tk

def on_click():
    print("Button clicked!")

root = tk.Tk()
btn = tk.Button(root, text="Click Me", command=on_click)
btn.pack()

root.mainloop()

8. Handling Events and User Input#

Events are user interactions (like button clicks or typing text).

Getting Input from Entry#

import tkinter as tk

def show_text():
    user_input = entry.get()
    label.config(text=f"Hello, {user_input}!")

root = tk.Tk()
entry = tk.Entry(root)
entry.pack()

btn = tk.Button(root, text="Submit", command=show_text)
btn.pack()

label = tk.Label(root, text="")
label.pack()

root.mainloop()

Explanation - entry.get() fetches text from the Entry widget. - label.config(text=“…”) updates the text dynamically.

9. Layout and Styling#

Tkinter offers geometry managers to position widgets.

Geometry Managers#

Manager

Description

pack()

Simplest, stacks widgets vertically/horizontally

grid()

Arranges widgets in a table-like structure

place()

Positions widgets using exact coordinates

12. Error Handling and Debugging in Tkinter#

Handling Invalid Inputs#

Use messagebox for displaying error messages.

from tkinter import messagebox

messagebox.showerror("Error", "Invalid input!")

Common Issues#

Problem

Cause

Solution

13. Packaging and Running#

Steps#

  1. Install PyInstaller:

pip install pyinstaller

  1. Build executable:

pyinstaller --onefile your_script.py

  1. Find the .exe file in the dist folder.

14. Mini GUI + API Projects (Practice Ideas)#

= 1 2 3 4 5 =

Example Tkinter Projects#

1. Simple Calculator#

Basic math operations using buttons and entry widget.

Key Concepts:

  • Button click events (bind)

  • eval() for expression evaluation

  • Dynamic Entry widget updates

2. Weather App (Using OpenWeatherMap API)#

Fetch weather data from an API and show it in GUI.

Key Concepts:

  • Integrating an API with Tkinter

  • Handling network requests ( requests )

  • Updating GUI elements dynamically

3. Random Cat Facts App#

Unit 2 : Multiple-Choice Questions (MCQs)#

Choose the correct option

  1. What is Tkinter in Python?

  1. A data analysis library

  2. A GUI library for building desktop applications

  3. A web framework

  4. A library for working with databases

  1. Which command creates the main application window in Tkinter?

  1. window = Tk()

  2. root = Tk()

  3. main = tk()

  4. main_window()

  1. Which function keeps the Tkinter window open and responsive?

  1. root.show()

  2. root.display()

  3. root.mainloop()

  4. root.loop()

  1. Which of the following is NOT a geometry manager in Tkinter?

  1. pack()

  2. grid()

  3. place()

  4. align()

  1. What does the ``command`` attribute in a Button widget do?

  1. To define the function to execute when clicked

  2. To change window size

  1. Which method retrieves the text from an Entry widget?

  1. .get()

  2. .text()

  3. .read()

  4. .fetch()

  1. What is the role of the Label widget?

  1. Accepts user input

  2. Displays text or images

  3. Displays menus

  4. Creates buttons

  1. Which module provides themed (modern) widgets in Tkinter?

  1. ttk

  2. themed

  3. modern_ui

  4. gui_theme

  1. What does ``pack()`` do in Tkinter?

  1. Defines exact position of widgets

  2. Organizes widgets into a window by stacking them

  3. Removes widgets from a window

  4. Closes the GUI

Answer Key: 1-b, 2-b, 3-c, 4-d, 5-a, 6-a, 7-b, 8-a, 9-b

Unit 2- Short Answer Questions#

Answer in 2–3 sentences.

  1. What is the purpose of the mainloop() function in Tkinter?

  2. Explain the difference between the pack() and grid() geometry managers.

  3. What does the command attribute in a Button do?

  4. How can you change the title of the Tkinter window?

  5. What is the difference between Label and Entry widgets?

  6. How can you organize multiple widgets inside a window neatly?

  7. What is ttk in Tkinter, and why is it used?

  8. How do you display a message box warning in Tkinter?

  9. How can you make the window size fixed so users can’t resize it?

  10. How do you close a Tkinter window programmatically?

Suggested Answers (for self-check):#

  1. Keeps the window open and listens for user events.

  2. pack() stacks widgets vertically/horizontally; grid() places them in rows and columns.

  3. Executes a function when the button is clicked.

  4. Using root.title("Window Title").

  5. Label shows text/images; Entry accepts one-line user input.

  6. Use frames, grid layout, or padding ( padx, pady).

  7. ttk gives modern, themed widgets.

  8. Using from tkinter import messagebox → messagebox.showwarning("Title", "Message").

  9. root.resizable(False, False)

  10. Using root.destroy()

Part C: Coding Exercises#

Exercise 1: Hello GUI#

Task:

Create a simple Tkinter window that displays the text:

Welcome to Tkinter!

and a button that closes the application when clicked.

Hint:

Use a [Label] for the text and [Button] with [root.destroy()].

Exercise 2: Greeting App#

Task:

Create a window with:

  • An Entry box for the user’s name

  • A Button that says “Greet Me”

  • A Label that displays [Hello, ] after the button is clicked

Expected Output:

Exercise 3: Simple Login Window#

Task:

Build a login form with:

  • Username and Password labels and entry boxes

  • A “Login” button that prints “Login Successful” in the console when clicked

Extra:

Use show="*" for password masking.

Exercise 4: Counter App#

Task:

Create a GUI counter with:

  • A label showing the number

  • “+” and “-” buttons to increase/decrease the count

Hint:

Use a variable and label.config(text=variable) to update the display.

Exercise 5: Color Changer#

Task:

Make a window with three buttons: “Red”, “Green”, and “Blue”.

Clicking each button should change the background color of the window.

Hint:

Use root.config(bg="color").

Exercise 6: Simple Calculator#

Task:

Create a GUI calculator that can add two numbers:

  • Two Entry fields for inputs

  • A “Calculate” button

  • A Label to show the result

Expected Output:

Contents