towary = {
    "cukier": 2,
    "chleb": 4,
    "jajka": 6
}

spis = ["cukier", "chleb", "jajka", "warzywa"]

def sprawdz(spis, towary):
    for x in spis:
        if not czyIstnieje(x,towary):
            print("brak towaru")

def czyIstnieje(produkt, towary):
    for key, value in towary.items():
        if(produkt == key):
            print(key, " = ", value)
            return True

    return  False

sprawdz(spis, towary)