Custom Decorators

Code

from functools import wraps
from flask import Flask, request, jsonify, g

app = Flask(__name__)

def require_api_key(view):
    @wraps(view)
    def wrapped(*args, **kwargs):
        key = request.headers.get("X-API-Key")
        if key != "secret":
            return jsonify({"error": "unauthorized"}), 401
        g.api_key = key
        return view(*args, **kwargs)
    return wrapped

def log_call(view):
    @wraps(view)
    def wrapped(*args, **kwargs):
        app.logger.info(f"{request.method} {request.path}")
        return view(*args, **kwargs)
    return wrapped

@app.route("/secure")
@require_api_key
@log_call
def secure():
    return jsonify({"ok": True, "key": g.api_key})

Explanation

Decorators wrap a view with functools.wraps to preserve metadata, then add behavior before or after the call. They can short-circuit by returning early, for example rejecting a missing API key, or stash data on g for the view to read. Stacking decorators runs them bottom-up when the route is invoked.

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