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Python urllib3 tutorial

Python urllib3 tutorial introduces the Python urllib3 module. We show how to grab data, post data, stream data, work with JSON, and use redirects.

ZetCode has also a concise Python tutorial.

The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web.

Python urllib3

The urllib3 module is a powerful, sanity-friendly HTTP client for Python. It supports thread safety, connection pooling, client-side SSL/TLS verification, file uploads with multipart encoding, helpers for retrying requests and dealing with HTTP redirects, gzip and deflate encoding, and proxy for HTTP and SOCKS.

$ pip install urllib3

We install the urllib3 module with pip.

Python urllib3 version

The first program prints the version of the urllib3 module.

version.py
#!/usr/bin/env python3

import urllib3

print(urllib3.__version__)

The program prints the version or urllib3.

$ ./version.py
1.24.1

This is a sample output of the example.

Python urllib3 status

HTTP response status codes indicate whether a specific HTTP request has been successfully completed. Responses are grouped in five classes:

status.py
#!/usr/bin/env python3

import urllib3


http = urllib3.PoolManager()

url = 'http://webcode.me'

resp = http.request('GET', url)
print(resp.status)

The example creates a GET request to the webcode.me. It prints the status code of the response.

http = urllib3.PoolManager()

We create a PoolManager to generate a request. It handles all of the details of connection pooling and thread safety.

url = 'http://webcode.me'

This is the URL to which we send the request.

resp = http.request('GET', url)

With the request() method, we make a GET request to the specified URL.

print(resp.status)

We print the status code of the response.

$ status.py
200

The 200 status code means that the request has succeeded.

Python urllib3 GET request

The HTTP GET method requests a representation of the specified resource.

get_request.py
#!/usr/bin/env python3

import urllib3


http = urllib3.PoolManager()

url = 'http://webcode.me'

resp = http.request('GET', url)
print(resp.data.decode('utf-8'))

The example sends a GET request to the webcode.me webpage. It returns the HTML code of the home page.

req = http.request('GET', url)

A GET request is generated.

print(resp.data.decode('utf-8'))

We get the data or the response and decode it into text.

$ ./get_request.py
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>My html page</title>
</head>
<body>

    <p>
        Today is a beautiful day. We go swimming and fishing.
    </p>

    <p>
         Hello there. How are you?
    </p>

</body>

This is the output.

Python urllib3 HEAD request

A HEAD request is a GET request without a message body.

head_request.py
#!/usr/bin/env python3

import urllib3


http = urllib3.PoolManager()

url = 'http://webcode.me'
resp = http.request('HEAD', url)

print(resp.headers['Server'])
print(resp.headers['Date'])
print(resp.headers['Content-Type'])
print(resp.headers['Last-Modified'])

In the example, we create a HEAD request to the webcode.me website.

print(resp.headers['Server'])
print(resp.headers['Date'])
print(resp.headers['Content-Type'])
print(resp.headers['Last-Modified'])

The response object contains the headers dictionary, which has the various header fields, such as server and date.

$ ./head_request.py
nginx/1.6.2
Thu, 20 Feb 2020 14:35:14 GMT
text/html
Sat, 20 Jul 2019 11:49:25 GMT

From the output we can see that the web server of the website is nginx and the content type is HTML code.

Python urllib3 HTTPS request

The urllib3 provides client-side TLS/SSL verification. For this, we need to download the certifi module. It is a carefully curated collection of Root Certificates for validating the trustworthiness of SSL certificates while verifying the identity of TLS hosts. It has been extracted from the Requests project.

$ pip install certifi

We install certifi.

import certifi

print(certifi.where())

To reference the installed certificate authority (CA) bundle, we use the built-in where() function.

status2.py
#!/usr/bin/env python3

import urllib3
import certifi


url = 'https://httpbin.org/anything'

http = urllib3.PoolManager(ca_certs=certifi.where())
resp = http.request('GET', url)

print(resp.status)

We create a GET request to the https://httpbin.org/anything page.

http = urllib3.PoolManager(ca_certs=certifi.where())

We pass the root CA bundle to the PoolManager. Without this CA bundle, the request would issue the following warning: InsecureRequestWarning: Unverified HTTPS request is being made. Adding certificate verification is strongly advised..

Python urllib3 query parameters

Query parameters are the part of a uniform resource locator (URL) which assigns values to specified parameters. This is one way of sending data to the destination server.

http://example.com/api/users?name=John%20Doe&occupation=gardener

The query parameters are specified after the ? character. Multiple fields are separated with the &. Special characters, such as spaces, are encoded. In the above string, the space is encoded with the %20 value.

query_params.py
#!/usr/bin/env python3

import urllib3
import certifi

http = urllib3.PoolManager(ca_certs=certifi.where())

payload = {'name': 'Peter', 'age': 23}

url = 'https://httpbin.org/get'
req = http.request('GET', url, fields=payload)

print(req.data.decode('utf-8'))

In the example, we send a GET request with some query parameters to the https://httpbin.org/get. The link simply returns some data back to the client, including the query parameters. The site is used for testing HTTP requests.

payload = {'name': 'Peter', 'age': 23}

This is the payload to be sent.

req = http.request('GET', url, fields=payload)

The query parameters are specified with the fields option.

$ ./query_params.py
{
  "args": {
    "age": "23",
    "name": "Peter"
  },
  "headers": {
    "Accept-Encoding": "identity",
    "Host": "httpbin.org",
    "X-Amzn-Trace-Id": "Root=1-5e4ea45f-c3c9c721c848f8f81a3129d8"
  },
  "origin": "188.167.251.9",
  "url": "https://httpbin.org/get?name=Peter&age=23"
}

The httpbin.org responded with a JSON string, which includes our payload as well.

Python urllib3 POST request

The HTTP POST method sends data to the server. It is often used when uploading a file or when submitting a completed web form.

post_request.py
#!/usr/bin/env python3

import urllib3
import certifi


http = urllib3.PoolManager(ca_certs=certifi.where())

url = 'https://httpbin.org/post'

req = http.request('POST', url, fields={'name': 'John Doe'})
print(req.data.decode('utf-8'))

The example sends a POST request. The data is specified with the fields option.

$ ./post_request.py
{
  "args": {},
  "data": "",
  "files": {},
  "form": {
    "name": "John Doe"
  },
  ...
  "url": "https://httpbin.org/post"
}

This is the output.

Python urllib3 send JSON

In requests, such as POST or PUT, the client tells the server what type of data is actually sent with the Content-Type header.

send_json.py
#!/usr/bin/env python3

import urllib3
import certifi
import json


http = urllib3.PoolManager(ca_certs=certifi.where())

payload = {'name': 'John Doe'}
encoded_data = json.dumps(payload).encode('utf-8')

resp = http.request(
     'POST',
     'https://httpbin.org/post',
     body=encoded_data,
     headers={'Content-Type': 'application/json'})

data = json.loads(resp.data.decode('utf-8'))['json']
print(data)

The example sends JSON data.

payload = {'name': 'John Doe'}
encoded_data = json.dumps(payload).encode('utf-8')

We encode the JSON data into binary format.

resp = http.request(
     'POST',
     'https://httpbin.org/post',
     body=encoded_data,
     headers={'Content-Type': 'application/json'})

We specify the Content-Type header in the request.

data = json.loads(resp.data.decode('utf-8'))['json']
print(data)

We decode the returned data back to text and print it to the console.

Python urllib3 binary data

In the following example, we download binary data.

get_binary.py
#!/usr/bin/env python3

import urllib3


http = urllib3.PoolManager()

url = 'http://webcode.me/favicon.ico'
req = http.request('GET', url)

with open('favicon.ico', 'wb') as f:
    f.write(req.data)

The example downloads a small icon.

with open('favicon.ico', 'wb') as f:
    f.write(req.data)

The req.data is in a binary format, which we can directly write to the disk.

Python urllib3 stream data

Chunked transfer encoding is a streaming data transfer mechanism available since HTTP 1.1. In chunked transfer encoding, the data stream is divided into a series of non-overlapping chunks.

The chunks are sent out and received independently of one another. Each chunk is preceded by its size in bytes.

Setting preload_content to False means that urllib3 will stream the response content. The stream() method iterates over chunks of the response content. When streaming, we should call release_conn() to release the http connection back to the connection pool so that it can be re-used.

streaming.py
#!/usr/bin/env python3

import urllib3
import certifi


url = "https://docs.oracle.com/javase/specs/jls/se8/jls8.pdf"

local_filename = url.split('/')[-1]

http = urllib3.PoolManager(ca_certs=certifi.where())

resp = http.request(
    'GET',
    url,
    preload_content=False)

with open(local_filename, 'wb') as f:

    for chunk in resp.stream(1024):
        f.write(chunk)

resp.release_conn()

In the example, we download a PDF file.

resp = http.request(
    'GET',
    url,
    preload_content=False)

With preload_content=False, we enable streaming.

with open(local_filename, 'wb') as f:

    for chunk in resp.stream(1024):
        f.write(chunk)

We iterate over the chunks of data and save them to a file.

resp.release_conn()

In the end, we release the connection.

Python urllib3 redirect

A redirect sends users and search engines to a different URL from the one they originally requested. To follow redirects, we set the redirect option to True.

redirect.py
#!/usr/bin/env python3

import urllib3
import certifi

http = urllib3.PoolManager(ca_certs=certifi.where())


url = 'https://httpbin.org/redirect-to?url=/'
resp = http.request('GET', url, redirect=True)

print(resp.status)
print(resp.geturl())
print(resp.info())

The example follows a redirect.

$ ./redirect.py
200
/
HTTPHeaderDict({'Date': 'Fri, 21 Feb 2020 12:49:29 GMT', 'Content-Type': 'text/html; 
charset=utf-8', 'Content-Length': '9593', 'Connection': 'keep-alive', 
'Server': 'gunicorn/19.9.0', 'Access-Control-Allow-Origin': '*', 
'Access-Control-Allow-Credentials': 'true'})

This is the output.

Python urllib3 Flask example

In the following example, we send a request to a small Flask web application.

$ pip install flask

We need to install the flask module.

app.py
#!/usr/bin/env python3

from flask import Flask
from flask import request


app = Flask(__name__)

@app.route('/headers')
def hello():

    ua = request.headers.get('user-agent')
    ka = request.headers.get('connection')

    return f'User agent: {ua}; Connection: {ka}'

The application has one route. It sends the user agent and connection header fields of a request to the client.

send_req.py
#!/usr/bin/env python3

import urllib3


http = urllib3.PoolManager()

url = 'localhost:5000/headers'

headers = urllib3.make_headers(keep_alive=True, user_agent='Python program')
resp = http.request('GET', url, headers=headers)
print(resp.data.decode('utf-8'))

In this program, we send a request to our Flask application.

url = 'localhost:5000/headers'

Flask runs on port 5000 by default.

headers = urllib3.make_headers(keep_alive=True, user_agent='Python program')

With the make_headers() helper method, we create a headers dictionary.

resp = http.request('GET', url, headers=headers)

We send a GET request to the URL; we specify the headers dictionary.

print(resp.data.decode('utf-8'))

We print the response to the terminal.

$ export FLASK_APP=app.py
$ flask run

We run the Flask application.

$ ./send_req.py
User agent: Python program; Connection: keep-alive

From a different terminal, we launch the send_req.py program.

In this tutorial, we have worked with the Python urllib3 module.

List all Python tutorials.