If value in list in python programming

I've been reading through a few posts in regards to checking for a value is in a list in python but can't seem to find any that relate to my scenario, it is as follows:

I need to be able to check for two things, if the item they have chosen is in the list and also if they can essentially afford the item in comparison to their bank balance which needs to change whenever something is purchased.

i am reading from a text file to get my list and seem to be having some trouble doing so as whenever i enter a piece of information from the list it says its not in it.

any help would be great thank you.