An assembly comprising a power line assembly and an electronic device to mate with the power line assembly, the electronic device comprising a built in battery and a power delivery assembly comprising power delivery contacts, the power line assembly comprising: a power line; a power line plug disposed at one end of the power line to mate with an outlet; and a power line base disposed at the other end of the power line and having surfaces at a top and a bottom, wherein each of the surfaces being provided with power-supply contacts, the power-supply contacts on the top or the bottom being configured to contact with the power-delivery contacts in the power-delivery assembly of the electronic device to supply power to the electronic device in response to the power line base mating the power-delivery assembly, the assembly being characterized in that the power delivery assembly of the electronic device is provided with a connection mating structure, and in that either of the surfaces at the top and the bottom of the power line base is provided with a connection structure for mating with the power-delivery assembly, wherein the power line assembly supports two power-supply modes comprising an attracted mode and a contacted mode, wherein in the attracted mode, the connection structure on either surface at the top or the bottom of the power line base mates with the connection mating structure in the power-delivery assembly to cause the power line base and the power-delivery assembly to be fixed to each other; and in the contacted mode, the other surface of the power line base contacts with the power-delivery assembly to cause non-fixed mating between the power line base and the power-delivery assembly. a power line; a power line plug disposed at one end of the power line to mate with an outlet; and a power line base disposed at the other end of the power line and having surfaces at a top and a bottom, wherein each of the surfaces being provided with power-supply contacts, the power-supply contacts on the top or the bottom being configured to contact with the power-delivery contacts in the power-delivery assembly of the electronic device to supply power to the electronic device in response to the power line base mating the power-delivery assembly, the assembly being characterized in that the power delivery assembly of the electronic device is provided with a connection mating structure, and in that either of the surfaces at the top and the bottom of the power line base is provided with a connection structure for mating with the power-delivery assembly, wherein the power line assembly supports two power-supply modes comprising an attracted mode and a contacted mode, wherein in the attracted mode, the connection structure on either surface at the top or the bottom of the power line base mates with the connection mating structure in the power-delivery assembly to cause the power line base and the power-delivery assembly to be fixed to each other; and in the contacted mode, the other surface of the power line base contacts with the power-delivery assembly to cause non-fixed mating between the power line base and the power-delivery assembly. in the attracted mode, the connection structure on either surface at the top or the bottom of the power line base mates with the connection mating structure in the power-delivery assembly to cause the power line base and the power-delivery assembly to be fixed to each other; and in the contacted mode, the other surface of the power line base contacts with the power-delivery assembly to cause non-fixed mating between the power line base and the power-delivery assembly.