Why is my python code giving me an error when there is more then one of the same file type?

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Summary

The issue arises when the script attempts to move files with the same extension, resulting in incorrect path manipulation and NotADirectoryError. The root cause is overwriting source_folder and destination_folder variables with file paths instead of maintaining directory paths.

Root Cause

  • Incorrect variable reassignment: source_folder and destination_folder are overwritten with file paths instead of staying as directories.
  • Path manipulation error: os.path.join is used incorrectly, treating file paths as directories.

Why This Happens in Real Systems

  • Lack of variable scope understanding: Junior engineers often reuse variables without considering their scope or purpose.
  • Insufficient testing: Edge cases like multiple files of the same type are not tested, leading to runtime errors.

Real-World Impact

  • Data loss: Files may be moved incorrectly or overwritten.
  • System instability: Errors can halt automation scripts, affecting productivity.
  • Debugging overhead: Time spent diagnosing and fixing issues delays project timelines.

Example or Code

import shutil
import os

home = '/home/mis1nput'
source_folder = home + '/Downloads/'

for filename in os.listdir(source_folder):
    if filename.endswith('.jpg'):
        destination_folder = home + '/Pictures'  # Fixed: Keep as directory
        src_file = os.path.join(source_folder, filename)  # Correct file path
        dst_file = os.path.join(destination_folder, filename)  # Correct destination
        shutil.move(src_file, dst_file)

How Senior Engineers Fix It

  • Maintain variable integrity: Use separate variables for directories and file paths.
  • Defensive programming: Add checks to ensure paths are valid before operations.
  • Modular design: Break the script into functions for clarity and reusability.

Why Juniors Miss It

  • Overlooking variable reuse: Juniors often reuse variables without understanding their original purpose.
  • Lack of path handling experience: Insufficient knowledge of file system operations leads to errors.
  • Skipping edge cases: Testing only trivial scenarios without considering real-world complexities.

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