This Short Tip Show How-to Check If a Package is Already Installed in Ubuntu Linux.
To the Article Bottom Link to Post Showing Exactly Howto Search for Files/Directories/Paths/Images by Command Line.
The Content and Details are Expressly Essentials to Give Focus Only to the Essentials Instructions and Commands and Make Tip Easier to Read & Digest ;)
- Open a Terminal Window
(Press “Enter” to Execute Commands)
dpkg -l [packagename]
For Example here Below the Output of a Check for python-django.