HTTP Requests

🌐 HTTP Requests: Your Python Messenger to the Internet

The Story: Meet Your Digital Postman

Imagine you want to send a letter to a friend across the world. You write your message, put it in an envelope, hand it to the postman, and wait for a reply. HTTP requests in Python work exactly the same way!

Your Python program is YOU. The internet is the world. And the requests library? That’s your super-fast digital postman who can deliver messages anywhere in milliseconds!

📬 Making GET Requests: “Hey, Can I See That?”

What is a GET Request?

Think of GET like walking up to a library and saying:

“Can I see the book about dinosaurs?”

You’re asking to look at something. You don’t change anything. You just want to read.

Simple Example

import requests

# Ask Google for their homepage
response = requests.get("https://www.google.com")

# Did we get it?
print(response.status_code)  # 200 means "Here you go!"

Real-World Example: Getting Weather

import requests

# Ask for weather data
url = "https://api.weather.com/today"
response = requests.get(url)

# Read what we got back
weather = response.json()
print(f"Today: {weather['temp']}°")

What Makes GET Special?

📮 Making POST Requests: “Here’s Something New!”

What is a POST Request?

POST is like mailing a package to someone:

“Hey, I’m sending you something new!”

You’re creating or submitting new data.

Simple Example: Sending a Message

import requests

url = "https://api.example.com/messages"

# The message we want to send
my_message = {
    "to": "friend@email.com",
    "text": "Hello from Python!"
}

# Send it!
response = requests.post(url, json=my_message)

print(response.status_code)  # 201 = "Created!"

The Difference: GET vs POST

graph TD
    A["You want data?"] --> B{What kind?}
    B --> |Read existing| C["Use GET"]
    B --> |Send new data| D["Use POST"]
    C --> E["Library: Show me a book"]
    D --> F["Library: Add my new book"]

Quick Comparison

📋 Request Headers: Your ID Badge

What Are Headers?

Imagine entering a building with special rooms. The security guard needs to know:

• Who are you?
• What language do you speak?
• What type of visitor are you?

Headers are your ID badge that tell the server about you!

Common Headers You’ll Use

import requests

url = "https://api.example.com/data"

# Your "ID badge" information
headers = {
    "Authorization": "Bearer my-secret-key",
    "Content-Type": "application/json",
    "User-Agent": "MyPythonApp/1.0"
}

response = requests.get(url, headers=headers)

What Each Header Means

Example: API with Authentication

import requests

api_key = "your-secret-key"

headers = {
    "Authorization": f"Bearer {api_key}",
    "Accept": "application/json"
}

response = requests.get(
    "https://api.github.com/user",
    headers=headers
)

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

📨 Response Handling: Reading Your Mail

What Do You Get Back?

When your postman returns, they bring back:

1. A status code - Did it work?
2. Headers - Extra info about the reply
3. Body - The actual content/data

Status Codes: The Quick Answer

import requests

response = requests.get("https://api.example.com")

# Check the status
if response.status_code == 200:
    print("Success! Here's your data.")
elif response.status_code == 404:
    print("Oops! Page not found.")
elif response.status_code == 500:
    print("Server had a problem.")

Understanding Status Codes

Reading the Response Body

import requests

response = requests.get("https://api.example.com/user")

# As plain text
text_data = response.text
print(text_data)

# As JSON (most APIs use this)
json_data = response.json()
print(json_data["name"])

# Response headers
print(response.headers["Content-Type"])

graph TD
    A["Send Request"] --> B["Get Response"]
    B --> C{Check Status}
    C --> |200-299| D["Read Body"]
    C --> |400-499| E["Fix Your Request"]
    C --> |500-599| F["Server Problem"]
    D --> G["Use the Data!"]

🔄 Session Objects: Your VIP Pass

The Problem Without Sessions

Imagine going to a theme park. Every single ride, you show your ticket. Get on, show ticket. Next ride, show ticket. Exhausting!

What if you had a wristband that proved you paid? Show it once, ride all day!

Sessions = Your Wristband

import requests

# Create your VIP wristband
session = requests.Session()

# Set it up once
session.headers.update({
    "Authorization": "Bearer my-token",
    "User-Agent": "MyApp/1.0"
})

# Now ALL requests use these automatically!
response1 = session.get("https://api.example.com/profile")
response2 = session.get("https://api.example.com/settings")
response3 = session.post("https://api.example.com/update")

# No need to add headers each time!

Why Use Sessions?

Session with Cookies (Login Example)

import requests

session = requests.Session()

# Login once
login_data = {
    "username": "me",
    "password": "secret"
}
session.post("https://site.com/login", data=login_data)

# Now you're logged in for ALL requests!
profile = session.get("https://site.com/my-profile")
orders = session.get("https://site.com/my-orders")
# Both work because session remembers you!

🛡️ Error Handling: When Things Go Wrong

Why Errors Happen

The internet isn’t perfect. Things go wrong:

• Website is down
• Your internet disconnected
• Request took too long
• Server rejected you

Good code handles these gracefully!

The Try-Except Pattern

import requests

try:
    response = requests.get(
        "https://api.example.com/data",
        timeout=5  # Wait max 5 seconds
    )
    response.raise_for_status()  # Raise error if bad status
    data = response.json()
    print(data)

except requests.exceptions.Timeout:
    print("Request took too long!")

except requests.exceptions.ConnectionError:
    print("Can't connect to internet!")

except requests.exceptions.HTTPError as e:
    print(f"HTTP error: {e}")

except requests.exceptions.RequestException as e:
    print(f"Something went wrong: {e}")

Common Errors You’ll See

graph TD
    A["Make Request"] --> B{Error?}
    B --> |No| C["Success!"]
    B --> |Timeout| D["Took too long"]
    B --> |ConnectionError| E["No internet"]
    B --> |HTTPError| F["Bad status code"]
    B --> |JSONDecodeError| G["Bad response format"]

Error Types Explained

The Safe Request Pattern

import requests

def safe_request(url):
    """Make a request that won't crash your program"""
    try:
        response = requests.get(url, timeout=10)
        response.raise_for_status()
        return response.json()

    except requests.exceptions.RequestException as e:
        print(f"Request failed: {e}")
        return None

# Use it safely
data = safe_request("https://api.example.com")
if data:
    print("Got data!", data)
else:
    print("Couldn't get data, try again later")

🎯 Putting It All Together

Here’s a complete example using everything you learned:

import requests

class APIClient:
    """A proper API client with all best practices"""

    def __init__(self, base_url, api_key):
        self.session = requests.Session()
        self.session.headers.update({
            "Authorization": f"Bearer {api_key}",
            "Content-Type": "application/json"
        })
        self.base_url = base_url

    def get(self, endpoint):
        """Safe GET request"""
        try:
            url = f"{self.base_url}{endpoint}"
            response = self.session.get(url, timeout=10)
            response.raise_for_status()
            return response.json()
        except requests.exceptions.RequestException as e:
            print(f"GET failed: {e}")
            return None

    def post(self, endpoint, data):
        """Safe POST request"""
        try:
            url = f"{self.base_url}{endpoint}"
            response = self.session.post(
                url, json=data, timeout=10
            )
            response.raise_for_status()
            return response.json()
        except requests.exceptions.RequestException as e:
            print(f"POST failed: {e}")
            return None

# Use it!
api = APIClient("https://api.mysite.com", "my-key")
user = api.get("/users/me")
new_post = api.post("/posts", {"title": "Hello!"})

🌟 You Did It!

You now understand:

• ✅ GET requests - Ask to see data
• ✅ POST requests - Send new data
• ✅ Headers - Your ID badge to the server
• ✅ Response handling - Read what comes back
• ✅ Sessions - Your VIP pass for multiple requests
• ✅ Error handling - Gracefully handle problems

You’re now ready to connect your Python programs to any API on the internet! 🚀

💡 Pro Tip: Always use timeout in your requests. Without it, your program could wait forever if a server doesn’t respond!