pythonadvanced3 hr est.
Python Web Scraper Project: Step-by-Step Code & Tutorial
Build an ethical, polite web scraper in Python using built-in urllib or requests to extract title headlines and structured data from sample HTML pages, format results into CSV, and respect robots.txt rules.
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Last updated: 2026-06-05
Before You Begin
- 1Understanding of HTML structure and DOM elements
- 2Familiarity with HTTP GET requests
- 3Understanding of string parsing or regular expressions
- 4Familiarity with Python CSV module
Project Architecture
Folder Structure
web_scraper/ ├── scraper.py ├── output.csv └── README.md
Data Flow
[Target URL] ➔ [robots.txt Check] ➔ [HTTP Request: HTML Fetch] ➔ [Parse Data Elements] ➔ [Format CSV Output]
Source Code Breakdown & Implementation
### Step 1: Project Setup
Create folder `web_scraper` and script `scraper.py`. We use `urllib.request` and `csv`.
### Step 2: Core Logic Implementation
Implement the HTML fetching function with custom User-Agent headers to ensure polite requests.
```python
import urllib.request
import urllib.error
import re
import csv
def fetch_html(url: string) -> string:
req = urllib.request.Request(
url,
headers={'User-Agent': 'Mozilla/5.0 (Education Bot)'}
)
with urllib.request.urlopen(req) as response:
return response.read().decode('utf-8')
```
### Step 3: Parsing & Exporting
Extract headlines and write to CSV.
```python
def parse_headlines(html: string) -> list:
# Extracting standard h2 tags using regex for demonstration
matches = re.findall(r'
(.*?)<\/h2>', html, re.DOTALL) clean = [re.sub(r'<.*?>', '', m).strip() for m in matches] return clean ```
### Step 4: Politeness & Exceptions
Always catch HTTP errors (404, 500) and respect crawl delays.
Complete Solution Code
Compare your approach
Testing Checklist
- • Run script against example.com.
- • Verify headings.csv is generated with extracted text.
- • Check error handling by inputting a broken URL.
Common Bugs
Bug: HTTP 403 Forbidden error.
Fix: Add User-Agent header to HTTP request.
Bug: UnicodeEncodeError when writing to CSV.
Fix: Use encoding='utf-8' when opening file.