Problem Solving – Fixing ReferenceError in Python When uploading files

ReferenceError in Python When Uploading Files

Explanation:

This error occurs when the code tries to access a variable (undefined_var) that hasn’t been defined in the current scope. In Python, all variables must be assigned before they are used.

Unlike JavaScript, Python doesn’t use the term “ReferenceError” officially, but a NameError is the closest equivalent, raised when a local or global name is not found.

In the context of uploading files, this could happen if you’re referencing a filename or file object that was never created or was conditionally initialized and is unavailable when accessed.

Fix / Workaround:

Make sure the variable is properly defined before use. Here’s an example:

uploaded_file = "example.txt"  # Define the variable

print(uploaded_file)  # Correct usage

In a file upload scenario using frameworks like Flask:
from flask import request

if 'file' in request.files:
    uploaded_file = request.files['file']
    print(uploaded_file.filename)
else:
    print("No file uploaded")

This ensures the variable exists before you use it.

References:

• Python Docs – Exceptions

• StackOverflow – Python NameError for undefined variables