micropython 4x4 matrix input

rows = [
    Pin(20, Pin.OUT), Pin(21, Pin.OUT), Pin(22, Pin.OUT), Pin(23, Pin.OUT),
]
columns = [
    Pin(16, Pin.IN), Pin(17, Pin.IN), Pin(18, Pin.IN), Pin(19, Pin.IN)
]

keys = [False] * 16
for r in rows:
    r.low()
code = ""
while True:
    for k in range(16):
        if keys[k] == True:
            lcd.putstr(str(k))
    time.sleep_ms(67)

    for r in range(4):
        rows[r].high()
        for c in range(4):
            if columns[c].value() == 1:
                keys[c * 4 + r] = True
            else:
                keys[c * 4 + r] = False
        rows[r].low()
    lcd.clear()

rows = [
    Pin(20, Pin.OUT), Pin(21, Pin.OUT), Pin(22, Pin.OUT), Pin(23, Pin.OUT),
]
columns = [
    Pin(16, Pin.IN), Pin(17, Pin.IN), Pin(18, Pin.IN), Pin(19, Pin.IN)
]

keys = [False] * 16
for r in rows:
    r.low()
code = ""
while True:
    for k in range(16):
        if keys[k] == True:
            lcd.putstr(str(k))
    time.sleep_ms(67)

    for r in range(4):
        rows[r].high()
        for c in range(4):
            if columns[c].value() == 1:
                keys[c * 4 + r] = True
            else:
                keys[c * 4 + r] = False
        rows[r].low()
    lcd.clear()