dev_appserver.py: command not found

Although I know that this question is marked resolved, I had the same issue. I tried to add the path to my .bashrc file, as suggested by Lipis, but the problem persisted.

I isolated the problem to needing to create symlinks. Not knowing how to do this, I found a workaround: install the GoogleAppEngineLauncher-1.9.40-OSX since the installation process gives the option to the user to automatically create symlinks along the way.

Once installed, you'll be able to make use of the deprecated application, but what's important is that you can now use dev_appserver.py and gcloud commands in the Terminal.

This error happens to me after a google software update. Open up GoogleAppEngineLauncher, and it will automatically fix the Command Symlinks so that you can use them again in the terminal. Well, you do have to click OK when the popup appears.

After downloading the App Engine source files you will have to add the directory in the path in order to be able to execute that script file.

Open your .bashrc file that is located in the home directory and this line with the correct path (read more):

export PATH=/path/to/google_app_engine/bin:$PATH