Turn an application or script into a shell command

Question

When I want to run my python applications from commandline (under ubuntu) I have to be in the directory where is the source code app.py and run the application with command
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Answer 1

1. Add a shebang line at the beginning of your file:

   #!/usr/bin/env python
   

2. Make your file executable by calling

   chmod +x app.py
   

   in the shell.

3. Move it to some location included in the PATH environment variable and rename it to app. Alternatively, add the path of the directory containing app to the PATH environment variable by adding the line

   export PATH=$PATH:/path/to/app
   

   to your .bash_profile.