When I try to import cv2 into python(command line)

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I tried importing cv2 into the python (command line) and got the following error message: "RuntimeError: module compiled against API version 0xa but this version of numpy is 0x7 Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: numpy.core.multiarray failed to import"

I don't know if I import into python idle, it will be any different. Problem is I can't even open my Python idle. Any help?