fix python isprime

isprime-python/Dockerfile

@@ -5,11 +5,11 @@ FROM python:3.7-slim
 # Copy local code to the container image.
 ENV APP_HOME /app
 WORKDIR $APP_HOME
-COPY . ./
 
 # Install production dependencies.
-RUN pip install Flask gunicorn
+RUN pip install --no-cache-dir Flask gunicorn
 
+COPY . ./
 # Run the web service on container startup. Here we use the gunicorn
 # webserver, with one worker process and 8 threads.
 # For environments with multiple CPU cores, increase the number of workers

isprime-python/app.py

@@ -4,10 +4,16 @@ from flask import Flask
 
 app = Flask(__name__)
 
+def safe_cast(val, to_type, default=107107):
+    try:
+        return to_type(val)
+    except (ValueError, TypeError):
+        return default
 
 @app.route('/')
 def isprime():
-    num = os.environ.get('TARGET', '107107')
+    num = safe_cast(os.environ.get('TARGET', 107107),int)
+
     if num > 1:
         for i in range(2, num):
             if (num % i) == 0: