Changed python documentation to use the onbuild example, similar to the ruby example.

python/README-content.md

@@ -15,18 +15,16 @@ Windows 2000 and later.
 
 ## Create a `Dockerfile` in your Python app project
 
-    FROM python:3
-    COPY . /usr/src/myapp
-    WORKDIR /usr/src/myapp
+    FROM python:3-onbuild
     CMD [ "python", "./your-daemon-or-script.py" ]
 
 or (if you need to use Python 2):
 
-    FROM python:2
-    COPY . /usr/src/myapp
-    WORKDIR /usr/src/myapp
+    FROM python:2-onbuild
     CMD [ "python", "./your-daemon-or-script.py" ]
 
+These images include multiple `ONBUILD` triggers which should be all you need to bootstrap most applications. The build will `COPY` a `requirements.txt` file, `RUN pip install` on said file, and then copy the current directory into `/usr/src/app`.
+
 You can then build and run the Docker image:
 
     docker build -t my-python-app

python/README.md

@@ -22,18 +22,16 @@ Windows 2000 and later.
 
 ## Create a `Dockerfile` in your Python app project
 
-    FROM python:3
-    COPY . /usr/src/myapp
-    WORKDIR /usr/src/myapp
+    FROM python:3-onbuild
     CMD [ "python", "./your-daemon-or-script.py" ]
 
 or (if you need to use Python 2):
 
-    FROM python:2
-    COPY . /usr/src/myapp
-    WORKDIR /usr/src/myapp
+    FROM python:2-onbuild
     CMD [ "python", "./your-daemon-or-script.py" ]
 
+These images include multiple `ONBUILD` triggers which should be all you need to bootstrap most applications. The build will `COPY` a `requirements.txt` file, `RUN pip install` on said file, and then copy the current directory into `/usr/src/app`.
+
 You can then build and run the Docker image:
 
     docker build -t my-python-app