TypeError: 'NoneType' object is not callable when using a nested function in Flask
I tried several approaches but none seem to work. I'm deploying to production and I'm relatively new to this, so bear with me. I'm working with a `TypeError` in my Flask application when trying to return a value from a nested function. The behavior message states `'NoneType' object is not callable`, which typically suggests I might be trying to call a function that isn't defined correctly. Here's a simplified version of what I have: ```python from flask import Flask, jsonify app = Flask(__name__) @app.route('/calculate/<int:num>', methods=['GET']) def calculate(num): def square(n): return n * n return jsonify(result=square(num)) if __name__ == '__main__': app.run(debug=True) ``` I was expecting to see a JSON response with the square of the number passed in the URL, but instead, I get the behavior when I access `/calculate/4`. I have verified that the `square` function is defined correctly within the `calculate` route. I've also checked that there are no other parts in my code that might shadow the `square` function name. Additionally, I tried moving the `square` function outside of `calculate`, but this led to a different behavior, indicating that the inner function's local scope was affecting the logic. What could be causing this scenario and how can I resolve it while maintaining the inner function design? My development environment is Windows. What's the best practice here? This is for a web app running on Linux. Am I missing something obvious? Thanks for any help you can provide!