404 Not Found

Hi Friends, I am new to Block chain. I am trying to learn block chain with the help of documentation provided here.
In blockchain.py file I have changed the following code:
app.run(host='0.0.0.0', port=port) to
app.run(host='127.0.0.1', port=port)
but instead of showing any results, it is displaying the 404 Not Found Error,
--- The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again.--

Any help in this regard would be highly appreciable.