Returns the average of a list, after mapping each element to a value using the provided function.
Use map()
to map each element to the value returned by fn
.
Use sum()
to sum all of the mapped values, divide by len(lst)
.
代码实现
def average_by(lst, fn=lambda x: x):
return sum(map(fn, lst), 0.0) / len(lst)
使用样例
average_by([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], lambda x: x['n']) # 5.0