merge_pdf.py

from PyPDF2 import PdfWriter      # Import PdfWriter class to create/merge PDF files
import os                        # Import os module to work with files and directories

merger = PdfWriter()             # Create a PdfWriter object to merge PDFs

files = [file for file in        # Create a list called 'files'
         os.listdir()            # Get all files/folders in the current directory
         if file.endswith(".pdf")]  # Keep only files that end with .pdf

for pdf in files:                # Loop through each PDF file in the list
    merger.append(pdf)           # Add (merge) the PDF into the PdfWriter object

merger.write("merged-pdf.pdf")   # Write all merged PDFs into a new file
merger.close()                   # Close the writer and release resources