f doesn't refer to anything.

iterating over the file object at all instead of just calling self.cache = openFile.readlines() means that calling strip() the line below removes data beyond just the trailing newlines.

The most obvious one:

    with open(self.file_path, 'r') as openFile:
        for line in f:

`f` does not exist. It should be `openFile`.

One is that the variable is called openFile and not f. I don't know enough python to see something else wrong with that but would love to know too, since I've written such a line just last week.