Fetch sales price from sales price list and put it into custom field


i wan’t to fetch sales price from price list in custom field in purchase invoice. I didn’t find any example how to do that. I try to put value Price List Name from sales price doctype but it give me error

We did this using a custom function written in app.

PY Function.

from erpnext.utilities.product import get_price

    def get_spare_price(item_code, price_list, customer_group, company):
        	price = get_price(item_code, price_list, customer_group, company)
        	return price

JS Code to call the function and set price.

frappe.ui.form.on("Quotation Optional Accessories", "accessory", function(frm, cdt, cdn) {
    var m = locals[cdt][cdn];
			method: "app_folder.api.get_spare_price",
			args: {
				item_code: m.accessory,
				price_list: frm.doc.selling_price_list,
				customer_group: frm.doc.customer_group,
				company: frm.doc.company
			callback: function(r) {
				rate = r.message["formatted_price"].split(" ")
				price = (rate[1].replace(',', ''))
				frappe.model.set_value(m.doctype, m.name, 'rate', price);
				frappe.model.set_value(m.doctype, m.name, 'price_list_rate', price);
	frm.add_fetch("stock_uom", "uom_name", "stock_uom");