Working with Network in Practice

4.1 Handling Responses

The requests module provides handy methods for working with server responses.

Status Codes

Besides the response, the server also sends a request processing status. Status info is available in the status_code and reason fields. Check out the example below:

import requests

response = requests.get('https://jsonplaceholder.typicode.com/posts/1')
print(response.status_code)  # Prints the status code of the response
print(response.reason)  # Prints the textual description of the status
print(response.ok)  # Returns True if the status code is less than 400
        

Headers

What's an HTTP request without headers, right? If you need the request headers or response headers, you can access them through the headers field:

import requests

response = requests.get('https://jsonplaceholder.typicode.com/posts/1')
print(response.headers)  # Prints the response headers
print(response.headers['Content-Type'])  # Prints the value of a specific header
            

Response Body

The server response can contain bytes, text, json, or xml. If you know what exactly you're requesting from the server, you can directly get an object of the desired type using one of the methods/fields:

import requests

response = requests.get('https://jsonplaceholder.typicode.com/posts/1')
print(response.text)  # Prints the response body as text
print(response.json())  # Prints the response body as JSON
print(response.content)  # Prints the response body as bytes
        

More details about headers and response statuses can be learned in networking lectures.

4.2 Error Handling

The requests module provides exceptions to handle errors.

The HTTP standard doesn't imply exceptions; instead, it uses error codes (status_code). If you want a Python exception to be thrown in case of a failed request, you need to explicitly call the function raise_for_status().

Example:

import requests

try:
    response = requests.get('https://jsonplaceholder.typicode.com/posts/1')
    response.raise_for_status()  # Raises exceptions for 4xx and 5xx status codes
except requests.exceptions.HTTPError as err:
    print(f"HTTP error occurred: {err}")
except Exception as err:
    print(f"Other error occurred: {err}")
else:
    print("Success!")
        

More details about error codes can be learned in networking lectures.

4.3 Sending Data

Before JSON was invented, large amounts of data were sent through "forms". A form is a special browser page object (and a data standard in HTTP). If you want to send data "via form", you just need to pass the data parameter along with the request.

Important! GET requests don't support forms as they don't have a request body. All their data is passed only in the URL.

Sending Data in a GET Request

In a GET request, data is passed through URL parameters. Here's an example:

import requests

params = {'key1': 'value1', 'key2': 'value2'}
response = requests.get('https://httpbin.org/get', params=params)
print(response.url)  # Prints the URL with added parameters
    

Sending Form Data

We're going to use a POST request to send data to the server.

Example:

import requests

data = {
    'username': 'example',
    'password': 'password'
}
response = requests.post('https://httpbin.org/post', data=data)
print(response.json())
        

Sending Files

If you want to send binary data over the internet, like uploading a picture, you need to pass your file or files in the request using the files parameter.

Example:

import requests

files = {'file': open('example.txt', 'rb')}
response = requests.post('https://httpbin.org/post', files=files)
print(response.json())
        

Easy as pie. If you want to send multiple files, just list them under any names in the files variable.

Important! Don't forget to close the file after sending to avoid resource leaks. It's best to use a with statement, which automatically closes the file after the operation:

import requests

with open('example.txt', 'rb') as f:
    files = {'file': f}
    response = requests.post('https://httpbin.org/post', files=files)
print(response.json())
        

4.4 Login and Authorization

API (Application Programming Interface) is a set of rules and protocols that allow different programs to interact with each other. Many websites and services only allow requests and API interactions after logging in.

After a successful login, you get a special object—a session (session), which contains a unique number of your "authorized session with the server". For further requests, you'll need to use this object.

Authentication

To log in to the server, you need to go through authentication (login process), for which you need to pass credentials with the request.

import requests
from requests.auth import HTTPBasicAuth
        
response = requests.get('https://httpbin.org/basic-auth/user/pass', \ 
                        auth=HTTPBasicAuth('user', 'pass'))
print(response.status_code)
        
    

This is how authorization looks, but it's usually used with a session.

Using Sessions

Sessions allow retaining parameters between requests, such as cookies or user authorization details.

import requests

payload = {
    'username': 'your_username',
    'password': 'your_password'
}
            
# Creating a session
session = requests.Session()
            
# Logging into the site
login_response = session.post('https://example.com/login', data = payload)
            
# Further actions as a logged-in user
data_response = session.get('https://example.com/api/data')
print(data_response.json())