prefix and environ

app.py

@@ -1,10 +1,17 @@
+import os
 from flask import Flask, render_template
 from flask_sock import Sock
+from . import prefix
 
-app = Flask(__name__)
+app = Flask(__name__, )
 sock = Sock(app)
 
 
+app.wsgi_app = prefix.PrefixMiddleware(
+    app.wsgi_app, prefix=os.environ.get("URL_PREFIX", "")
+)
+
+
 @app.route('/')
 def index():
     return render_template('index.html')

prefix.py

@@ -0,0 +1,14 @@
+class PrefixMiddleware(object):
+    def __init__(self, app, prefix=""):
+        self.app = app
+        self.prefix = prefix
+
+    def __call__(self, environ, start_response):
+
+        if environ["PATH_INFO"].startswith(self.prefix):
+            environ["PATH_INFO"] = environ["PATH_INFO"][len(self.prefix) :]
+            environ["SCRIPT_NAME"] = self.prefix
+            return self.app(environ, start_response)
+        else:
+            start_response("404", [("Content-Type", "text/plain")])
+            return ["This url does not belong to the app.".encode()]