A system comprising a device for assisting a purchase by a customer at a self-service retail point of sale , said device including: - a central portion , - a handle that is linked to the central portion ; - suspension arms which are connected to the central portion and extend on either side of the central portion , said suspension arms being intended to be connected to a portable container provided with an opening enabling an item offered for sale at the point of sale to be placed in this portable container so as to allow said portable container to be carried by the device , the central portion facing said opening when said device is being used to carry the portable container , the suspension arms being designed to hold the portable container open; - at least one movement sensor which is configured to detect a movement through the opening of the portable container , when said device is being used to carry the portable container , - at least one image sensor which is configured to detect at least one image of a scene at least partially covering the opening, when said device is being used to carry the portable container and the movement sensor has detected a movement through said opening, - a position sensor which is configured to determine the current position of said device in the point of sale , the system also including: - processing means provided with information on a list of items offered for sale at the point of sale and that are configured to recognize, with a predetermined confidence level, an item appearing in said at least one image, this item being recognized from a reduced list of items included in said list of items , this reduced list of items comprising the items of said list of items whose locations in the point of sale are close to a position of said device determined by the position sensor . - a central portion , - a handle that is linked to the central portion ; - suspension arms which are connected to the central portion and extend on either side of the central portion , said suspension arms being intended to be connected to a portable container provided with an opening enabling an item offered for sale at the point of sale to be placed in this portable container so as to allow said portable container to be carried by the device , the central portion facing said opening when said device is being used to carry the portable container , the suspension arms being designed to hold the portable container open; - at least one movement sensor which is configured to detect a movement through the opening of the portable container , when said device is being used to carry the portable container , - at least one image sensor which is configured to detect at least one image of a scene at least partially covering the opening, when said device is being used to carry the portable container and the movement sensor has detected a movement through said opening, - a position sensor which is configured to determine the current position of said device in the point of sale , - processing means provided with information on a list of items offered for sale at the point of sale and that are configured to recognize, with a predetermined confidence level, an item appearing in said at least one image, this item being recognized from a reduced list of items included in said list of items , this reduced list of items comprising the items of said list of items whose locations in the point of sale are close to a position of said device determined by the position sensor . <EOS>