Find the most expensive item from the given list using Python.
[{'item': 'rice', 'price': 22.20}, {'item': 'bread', 'price': 15.00}, {'item': 'milk', 'price': 18.60}, {'item': 'butter', 'price': 34.40}]
most_expensive_item = max(list_of_items, key=lambda x: x['price'])