MicroPython 74HC595 flowing light on an LED bar, on an ESP32-DevKitC V4

# Flowing water light through a 74HC595: one lit LED walks along the
# eight outputs and back, three GPIOs doing the work of eight.
from hc595 import HC595
import time

chip = HC595(14, 12, 13)      # DS on 14, ST_CP on 12, SH_CP on 13

while True:
    for i in range(8):
        chip.write(1 << i)
        time.sleep_ms(300)
    for i in range(6, 0, -1):
        chip.write(1 << i)
        time.sleep_ms(300)
    print("back and forth")

# hc595.py: send a byte to a 74HC595 on three pins.
# data is DS, latch is ST_CP and clock is SH_CP. Each bit is set on DS
# and clocked in on a rising SH_CP; a rising ST_CP shows all eight.
from machine import Pin

class HC595:
    def __init__(self, data, latch, clock, oe=None):
        self.data = Pin(data, Pin.OUT, value=0)
        self.latch = Pin(latch, Pin.OUT, value=0)
        self.clock = Pin(clock, Pin.OUT, value=0)
        if oe is not None:
            self.oe = Pin(oe, Pin.OUT, value=0)    # OE low: the outputs are on

    def shift(self, value, msb_first=True):
        for i in range(8):
            bit = 7 - i if msb_first else i
            self.data.value((value >> bit) & 1)
            self.clock.value(1)
            self.clock.value(0)

    def write(self, value, msb_first=True):
        self.latch.value(0)
        self.shift(value, msb_first)
        self.latch.value(1)