self.qcpbars = QCPBars(x_axis, y_axis)

self.qcpbar_data = QCPBarsDataContainer() <== first data
self.qcpbars.setData(self.qcpbar_data)

self.qcpbars.data().clear() <== meaningless whether it is present or absent

self.qcpbar_data2 = QCPBarsDataContainer() <== second data
self.qcpbars.setData(self.qcpbar_data2)

del self.qcpbar_data <= Delete first data, Program crash occurred

Could you please help me?