Abstract: A lamp for a light string has a socket, multiple electric cords, an insulating partition, a leaf spring and a bulb assembly. The electric cords are mounted in the socket and have electrodes. The insulating partition is mounted in the socket and has a cavity and at least one stopper formed in the cavity. The leaf spring is mounted in the insulating partition, is V shaped, is held in place by the stopper and protrudes through a top of the insulating partition to selectively and respectively contact the electrodes. The bulb assembly is removably plugged into the socket and has a separator. The separator pushes the leaf spring into the insulating partition to stop the leaf spring from contacting the electrodes. When the bulb assembly is removed from the socket, the leaf spring returns to an original shape by resilience to contact the electrodes.