How to Specify URI to a local File in PyGtk LinkButton

I need to create a link button (gtk.LinkButton) with an URI to a local file. Does anyone know what is a valid URI format for a local file ? I want to specify a relative folder example: ../some_folder/file_i_need_to_open.txt

If this is can't be done, I don't mind putting the file in the same folde开发者_如何学运维r as the python source code =)

Thank you.

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Something like: file:///usr/bin/ is generally used for local URI. But maybe just /usr/bin/ works too. Have you tried it?