# Voegt de (geordende) bestanden transacties-1.txt en transacties-2.txt samen
# tot één enkel bestand.
with open("transacties-1.txt", "r") as bestand_1:
    with open("transacties-2.txt", "r") as bestand_2:
        with open("transacties.txt", "w") as bestand_3:

            # hoofdlus
            regel_1 = bestand_1.readline()
            regel_2 = bestand_2.readline()

            while regel_1 and regel_2: # zolan
                if regel_1 < regel_2:
                    print(regel_1, file = bestand_3, end='')
                    regel_1 = bestand_1.readline()
                else:
                    print(regel_2, file = bestand_3, end='')
                    regel_2 = bestand_2.readline()

            # behandel wat er overblijft van bestand_1
            while regel_1:
                print(regel_1, file = bestand_3, end='')
                regel_1 = bestand_1.readline()

            # behandel wat er overblijft van bestand_1
            while regel_2:
                print(regel_2, file = bestand_3, end='')
                regel_2 = bestand_2.readline()