[Tutor] Novice Python Question

[S Potter]

To whom it may concern;
 
I am a just experimenting with Python and learning as I go. The majority of my stumbling blocks have been syntax. So with that I must ask a couple of technical albeit probably very simple questions. Hopefully, you may provide me some insight and help me on my way.
 
Question 1.) 
    I have dictionary or list containing multiple  instances 'duplicate entries' of the same information. Lets say it's a list of addresses and list item i[0] contains city values equal to 'Albany' . 
    
    I am using a second list of one element to provide my filter criteria. This list contains only cities with no duplicate entries.
 
    How do I filter my first list based upon the selected position or a variable equal to the value of the selected position from my second list? 
 
Question 2.) If I assign a value to a variable x = "MyVlaue"
                    How do I put the value of  x into a list? 
                            I would think it would be something like:
                                    list[(str(x))]
                            But I'm not getting the results I expect. 
                            This would probably be considered macro-substitution in other languages but I cannot find reference to this in python.
 
Your help is greatly appreciated.
 
Thank you in advanced,
 
S.
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