Build a PDF Diff Checker in Python (Text + Visual Differences)

Sergey Kovalchuk — Wed, 27 Aug 2025 09:20:19 +0000

Have you ever needed to compare two PDFs — like contracts, reports, or generated docs?
Text diffs are useful, but sometimes you also need visual differences.

Here’s a minimal Python approach

1. Extract text and compare

import difflib
from PyPDF2 import PdfReader

def get_text(path):
    reader = PdfReader(path)
    return [page.extract_text() for page in reader.pages]

pdf1_text = get_text("file1.pdf")
pdf2_text = get_text("file2.pdf")

diff = difflib.unified_diff(pdf1_text, pdf2_text)
print("\n".join(diff))

2. Visual comparison (page by page)

from pdf2image import convert_from_path
from PIL import ImageChops

pages1 = convert_from_path("file1.pdf")
pages2 = convert_from_path("file2.pdf")

for i, (p1, p2) in enumerate(zip(pages1, pages2)):
    diff_img = ImageChops.difference(p1, p2)
    diff_img.save(f"diff_page_{i+1}.png")

Now you get diff PNGs highlighting changes.

Why this matters:

QA teams can validate reports
Lawyers can compare contract revisions
Developers can check generated PDFs

In my full article I explain how to:

combine text + visual diffs
highlight changes in generated PDFs
wrap it in FastAPI (for micro-SaaS or team use)

📖 Read the full guide here: Building a PDF Diff Checker in Python

Evolution of Python Functions: From 2.7 to 3.12 (with Code Examples)

Sergey Kovalchuk — Wed, 27 Aug 2025 09:10:11 +0000

Python has come a long way since 2.7.
Back then:

print was still a statement
type hints didn’t exist
% formatting was the default

Today, we write functions very differently.

# Python 2.7
def greet(name):
    print "Hello, %s" % name

# Python 3.10+
def greet(name: str) -> str:
    return f"Hello, {name}"

And with Python 3.12, we even get more concise typing with list[str], | for unions, and better error messages.

In my full article, I walk through:

Type hints (from typing.List[str] → list[str])
F-strings replacing % and .format()
Structural Pattern Matching (Python 3.10)
Why print had to change from statement → function

Read the full deep dive on Medium: Evolution of Functions in Python: From Python 2.7 to Today

DEV Community: Sergey Kovalchuk

Build a PDF Diff Checker in Python (Text + Visual Differences)

Evolution of Python Functions: From 2.7 to 3.12 (with Code Examples)