Error Handling

Code

from flask import Flask, jsonify, render_template, request

app = Flask(__name__)

@app.errorhandler(404)
def not_found(error):
    if request.path.startswith("/api/"):
        return jsonify({"error": "not found", "code": 404}), 404
    return render_template("404.html"), 404

@app.errorhandler(500)
def server_error(error):
    app.logger.exception("Internal error")
    return render_template("500.html"), 500

@app.errorhandler(ZeroDivisionError)
def handle_zero(error):
    return "cannot divide by zero", 400

@app.route("/boom")
def boom():
    return 1 / 0

Explanation

errorhandler() registers a function for a specific HTTP status code or exception class. Handlers return a response just like views and can branch on the request path to serve JSON or HTML. Logging inside 500 handlers preserves the traceback before it is converted to a response.

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