difflib.context_diff(a, b, fromfile='', tofile='', fromfiledate='', tofiledate='', n=3, lineterm='\n')
Compare a and b (lists of strings); return a delta (a generator generating the delta lines) in context diff format.
Context diffs are a compact way of showing just the lines that have changed plus a few lines of context. The changes are shown in a before/after style. The number of context lines is set by n which defaults to three.
By default, the diff control lines (those with *** or ---) a