title: Python virtual environment, can't find '__main__' module in
body: <p>I am studying Flask,with my first book example I have encountered problem</p>
  
  <pre><code>&gt;&gt;&gt; from flask import Flask
  &gt;&gt;&gt; app = Flask(__name__)
  &gt;&gt;&gt; @app.route('/')
  ... def index():
  ...     return '&lt;h1&gt;Hello World!&lt;/h1&gt;'
  ... 
  &gt;&gt;&gt; if __name__ == '__main__':
  ...     app.run(debug=True)
  ... 
   * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
   * Restarting with stat
  /home/tati/flasky/venv/bin/python: can't find '__main__' module in ''
  (venv) tati@tati-System-Product-Name:~/flasky$ python --version
  Python 2.7.12
  </code></pre>
  
  <p>My Python venv is 2.7.Does this creates havoc or not?
  If I go out,from command line(conda python installation)</p>
  
  <pre><code>python --version
  Python 3.6.0 :: Anaconda custom (64-bit)
  </code></pre>
  
  <p>How can I solve this?</p>