humanized_tabular_diff

def humanized_diff(L, delta):
    """
    Convert the given (sorted!!) tabular diff to a string,
     marked up with +s and -s, similar to regular diff(1)'s "-u" mode.
    """
    D, A = delta
    
    U, D = drop(L, D), [L[i] for i in D]
    
    def prefix(v, S):
        return [(v,s) for s in S]
    
    A = prefix("+", A)
    D = prefix("-", D)
    U = prefix(" ", U)
    
    R = merge(A,D,U, key=lambda v: v[1])
    
    R = ["%s%s" % (r[0], r[1]) for r in R]
    return str.join("\n", R)