30-seconds-of-code/snippets/average_by.md

title, tags

title	tags
average_by	math,list,function,intermediate

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).

def average_by(lst, fn=lambda x: x):
  return sum(map(fn, lst), 0.0) / len(lst)

average_by([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], lambda x: x['n']) # 5.0