n1 We hereinafter refer to the cited statute as "section 580b" or as "the statute." The language thereof which controls the present case appears in its text as amended in 1963 (Stats. 1963, ch. 2158, @ 1, p. 4500) to provide in pertinent part as follows (with the 1963 amendment shown by italics): "No deficiency judgment shall lie in any event after any sale of real property for failure of the purchaser to complete his contract of sale, or under a deed of trust, or mortgage, given to the vendor to secure payment of the balance of the purchase price of real property, or under a deed of trust, or mortgage, on a dwelling for not more than four families given to a lender to secure repayment of a loan which was in fact used to pay all or part of the purchase price of such dwelling occupied, entirely or in part, by the purchaser."  . . .