data_list = []
def data_item(func):
  data_list.append(func)
  return func
@data_item
def foo():
  return 1
@data_item
def foo1():
  return 2
@data_item
def foo3():
  return 3
def max_item():
  result = max(i() for i in data_list)
  return result
if __name__ == '__main__':
  item = max_item()
  print(item)

[<function foo at 0x10bb05ea0>, <function foo1 at 0x10bb05d90>, <function foo3 at 0x10bb05f28>]

max(i() for i in data_list)