How to set on executable bit for a particular file automatically

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http://unix.stackexchange.com – I want that when i make create a particular file, suppose i create it in vim editor, the created file should get executable permission as well when it gets created . I want this as i am creating some python files and don't want to explicitly set permissions for the file so i want some way so that executable bit is set as soon i create a file with particular extension or with a particular editor. (HowTos)