INTRO   O

PROBLEM SOLVING AND

PROGRAMMING IN PYTHON

 

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Prof. Andrea Gallegati
tuj81353@temple.edu

Prof. Dario Abbondanza
tuk96119@temple.edu

CIS 1051 - APIs

Understanding APIs
in Python

What Is an API ?

Imagine you order a coffee at a café:

  • You ask the barista for a coffee.
  • The barista prepares it.
  • You receive the coffee.

APIs (Application Programming Interface) works the same way:

  • You request something.
  • The system processes it.
  • You receive the result.

Why Do We Need APIs?

Allow different programs to communicate efficiently.


They  bridge between software components, making reusability, modularity, and automation easier.

... in a word integration !

✅ Operating System APIs

  • Python code interacts with file systems: 
    open(), read(), write()

✅ Library APIs

  • import and use pre-built functions from modules.

Examples: APIs in Everyday Life

with open("file.txt", "r") as file:
    data = file.read()
print(data)
import math

# Uses math API to 
# calculate the square root

print(math.sqrt(25))

✅ Hardware APIs

  • Programs interact with sensors, cameras, or printers.

Examples: APIs in Everyday Life

import RPi.GPIO as GPIO

# Turn on a device connected to pin 18

GPIO.output(18, GPIO.HIGH)

APIs make software modular

no need to rebuild everything from scratch!

Web APIs:

Extending APIs to the Internet

A Web API allows:

  • Programs to request data from online services.
     
  • Websites, apps, and databases to "talk" to each other.
     
  • Integration of third-party services 
    (Google Maps, Twitter, etc.).

💡 Example: Weather Apps

  • You type "Weather in Rome" in a weather app.
  • The app sends a request to a weather API.
  • The API returns the temperature, humidity, etc.

HTTP Requests:

Communicating with Web APIs

APIs on the web use HTTP requests to exchange data.

Types of HTTP Requests

Method What It Does
GET Retrieve data (e.g., weather, user details)
POST Send new data (e.g., register a user)
PUT Update existing data (e.g., change user email)
DELETE Remove data (e.g., delete a user account)

Example: GET Request (Fetching Data)

🔹 This requests GitHub API data and prints the response.

import requests

response = requests.get("https://api.github.com")
print(response.json())  # Convert response to a dictionary

REST APIs vs. Non-REST APIs

Most modern APIs follow the REST model (Representational State Transfer), but not all.

REST API Characteristics

✅ Uses standard HTTP methods (GET, POST, etc.).
✅ Returns structured data (usually JSON).
✅ Stateless (each request does not depend on previous ones).

Example: REST API
(Fetching User Data)

🔹 This fetches user information from a public API.

import requests

url = "https://jsonplaceholder.typicode.com/users/1"
response = requests.get(url)

print(response.json())  # Display user data

https://jsonplaceholder.typicode.com/

Non-REST APIs:

When REST Isn't Enough

Some APIs don’t follow REST principles. Examples are:

  • GraphQL APIs (Flexible queries instead of fixed endpoints).
  • WebSockets (Live, two-way communication).
  • RPC-based APIs (Remote Procedure Calls, like gRPC).

Example: GraphQL Query

🔹 This fetches country data using GraphQL.

https://countries.trevorblades.com/​

import requests

url = "https://countries.trevorblades.com/"
query = {"query": "{ country(code: \"IT\") { name, capital } }"}

response = requests.post(url, json=query)
print(response.json())

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