17. 解决方案：Lambda 表达式
练习解决方案：Lambda 与 Map
numbers = [
[34, 63, 88, 71, 29],
[90, 78, 51, 27, 45],
[63, 37, 85, 46, 22],
[51, 22, 34, 11, 18]
]
averages = list(map(lambda x: sum(x) / len(x), numbers))
print(averages)输出：
[57.0, 58.2, 50.6, 27.2]练习解决方案：Lambda 与 Filter
cities = ["New York City", "Los Angeles", "Chicago", "Mountain View", "Denver", "Boston"]
short_cities = list(filter(lambda x: len(x) < 10, cities))
print(short_cities)输出：
['Chicago', 'Denver', 'Boston']