>>804
同じkeyがあれば上書きされるだけ

In : csvlist = [[1, 2], [1, 2], [2, 3], [4, 5], [1, 2], [2, 3]]
In : dic = {(1, 2): 0, (2, 3): 0, (4, 5): 0}

In : dic={(s[0],s[1]):dic[(s[0],s[1])]+1 for s in csvlist}
In : dic
Out: {(1, 2): 1, (2, 3): 1, (4, 5): 1}

In : dic={(s[0],s[1]):dic[(s[0],s[1])]+1 for s in csvlist}
In : dic
Out: {(1, 2): 2, (2, 3): 2, (4, 5): 2}