如何从列表项更新字典？

你应该看一下计数器:

from collections import Counter

inventory = {'rope': 1, 'torch':6, 'gold coin':42, 'dagger': 1, 'arrow': 12}
inventory_ctr = Counter(inventory)

update = ['rope', 'torch']
update_ctr = Counter(update)

new_inventory_ctr = inventory_ctr + update_ctr

print(new_inventory_ctr)