Python Networking — requests, urllib & sockets

Networking in Python spans two levels: high-level HTTP (talking to web APIs and sites) and low-level sockets (raw TCP/UDP connections). Most apps live at the HTTP level.

Tool	Level	Notes
`requestsrequests`	High (HTTP)	Third-party, the de-facto standard. `pip install requestspip install requests`.
`urllib.requesturllib.request`	High (HTTP)	Built in; more verbose, no install needed.
`urllib.parseurllib.parse`	Helper	Build and parse URLs (pure, no network).
`socketsocket`	Low (TCP/UDP)	Raw connections; build your own protocols.

requests — the friendly HTTP client

requestsrequests makes HTTP calls readable. Install it first (pip install requestspip install requests).

requests_get.py

import requests
 
resp = requests.get("https://api.example.com/users", params={"page": 2})
print(resp.status_code)     # 200
print(resp.headers["Content-Type"])
data = resp.json()          # parse a JSON body into Python
print(data)

requests_get.py

import requests
 
resp = requests.get("https://api.example.com/users", params={"page": 2})
print(resp.status_code)     # 200
print(resp.headers["Content-Type"])
data = resp.json()          # parse a JSON body into Python
print(data)

requests_post.py

import requests
 
# Send JSON in the body
resp = requests.post(
    "https://api.example.com/users",
    json={"name": "Ada", "role": "admin"},
    headers={"Authorization": "Bearer TOKEN"},
    timeout=10,
)
resp.raise_for_status()     # raise if status is 4xx/5xx
print(resp.json())

requests_post.py

import requests
 
# Send JSON in the body
resp = requests.post(
    "https://api.example.com/users",
    json={"name": "Ada", "role": "admin"},
    headers={"Authorization": "Bearer TOKEN"},
    timeout=10,
)
resp.raise_for_status()     # raise if status is 4xx/5xx
print(resp.json())

`requestsrequests` piece	Purpose
`requests.get/post/put/deleterequests.get/post/put/delete`	The HTTP verbs.
`params={...}params={...}`	Query-string parameters.
`json={...}json={...}`	Send a JSON body.
`headers={...}headers={...}`	Custom request headers.
`resp.status_coderesp.status_code`	The HTTP status (200, 404, …).
`resp.json()resp.json()` / `resp.textresp.text`	Parsed JSON / raw text.
`resp.raise_for_status()resp.raise_for_status()`	Turn error statuses into exceptions.
`timeout=timeout=`	Fail fast instead of hanging forever.

urllib — the standard-library option

When you can’t add dependencies, urllib.requesturllib.request does the same job with more ceremony.

urllib_get.py

import urllib.request
import json
 
req = urllib.request.Request(
    "https://api.example.com/data",
    headers={"User-Agent": "my-app"},
)
with urllib.request.urlopen(req, timeout=10) as resp:
    body = resp.read().decode("utf-8")
    data = json.loads(body)
print(data)

urllib_get.py

import urllib.request
import json
 
req = urllib.request.Request(
    "https://api.example.com/data",
    headers={"User-Agent": "my-app"},
)
with urllib.request.urlopen(req, timeout=10) as resp:
    body = resp.read().decode("utf-8")
    data = json.loads(body)
print(data)

urllib.parse — build and parse URLs

This part of urlliburllib is pure (no network) and extremely useful for assembling query strings and dissecting URLs.

urllib_parse.py

from urllib.parse import urlencode, urlparse, parse_qs
 
# Build a query string from a dict
qs = urlencode({"q": "python", "page": 2})
print(qs)                     # q=python&page=2
 
# Dissect a URL
parts = urlparse("https://example.com/search?q=python&page=2")
print(parts.scheme)           # https
print(parts.netloc)           # example.com
print(parts.path)             # /search
print(parse_qs(parts.query))  # {'q': ['python'], 'page': ['2']}

urllib_parse.py

from urllib.parse import urlencode, urlparse, parse_qs
 
# Build a query string from a dict
qs = urlencode({"q": "python", "page": 2})
print(qs)                     # q=python&page=2
 
# Dissect a URL
parts = urlparse("https://example.com/search?q=python&page=2")
print(parts.scheme)           # https
print(parts.netloc)           # example.com
print(parts.path)             # /search
print(parse_qs(parts.query))  # {'q': ['python'], 'page': ['2']}

socket — low-level TCP

For custom protocols or learning how the network really works, use raw sockets. Here’s a minimal echo server and client.

tcp_server.py

import socket
 
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(("127.0.0.1", 9000))
server.listen()
print("listening on 9000")
 
conn, addr = server.accept()      # blocks until a client connects
with conn:
    data = conn.recv(1024)        # read up to 1024 bytes
    conn.sendall(data)            # echo it back

tcp_server.py

import socket
 
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(("127.0.0.1", 9000))
server.listen()
print("listening on 9000")
 
conn, addr = server.accept()      # blocks until a client connects
with conn:
    data = conn.recv(1024)        # read up to 1024 bytes
    conn.sendall(data)            # echo it back

tcp_client.py

import socket
 
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.connect(("127.0.0.1", 9000))
    s.sendall(b"hello")
    reply = s.recv(1024)
print(reply)                      # b'hello'

tcp_client.py

import socket
 
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.connect(("127.0.0.1", 9000))
    s.sendall(b"hello")
    reply = s.recv(1024)
print(reply)                      # b'hello'

socket call	Purpose
`socket(AF_INET, SOCK_STREAM)socket(AF_INET, SOCK_STREAM)`	Create a TCP socket.
`bind((host, port))bind((host, port))`	Attach a server to an address.
`listen()listen()` / `accept()accept()`	Wait for and accept a connection.
`connect((host, port))connect((host, port))`	Client connects to a server.
`sendall(bytes)sendall(bytes)` / `recv(n)recv(n)`	Send / receive raw bytes.

Sockets speak bytes, not strings — encode with .encode().encode() and decode with .decode().decode().

Choosing a level

decision.txt

Talking to a web API or website?   -> requests (or urllib if no installs)
Just building/parsing a URL?       -> urllib.parse
Custom protocol / raw TCP/UDP?     -> socket

decision.txt

Talking to a web API or website?   -> requests (or urllib if no installs)
Just building/parsing a URL?       -> urllib.parse
Custom protocol / raw TCP/UDP?     -> socket

Common pitfalls

No timeout — network calls can hang forever; always pass timeout=timeout=.
Ignoring status codes — check resp.status_coderesp.status_code or call raise_for_status()raise_for_status().
Sending strings over sockets — sockets need bytes; encode/decode explicitly.
requestsrequests isn’t built in — it needs pip install requestspip install requests; urlliburllib does not.

Practice Exercises

These exercises use urllib.parseurllib.parse, which runs without any network access.

Exercise 1 – Build a query string

Exercise 2 – Extract the host from a URL

Exercise 3 – Parse query parameters

Summary

For HTTP, reach for requestsrequests (clean API) or urllib.requesturllib.request (built in, verbose).
Always set a timeouttimeout and check the status code.
urllib.parseurllib.parse builds and dissects URLs with urlencodeurlencode, urlparseurlparse, and parse_qsparse_qs.
socketsocket gives raw TCP/UDP for custom protocols — remember it speaks bytes.
Pick the level that matches the task: APIs → requests, URLs → urllib.parse, raw connections → socket.

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