Python map object getting exhausted/consumed?

Question

Backdrop

While fiddling with the map() function in my Python project, I tried to assign a variable, the python map object I intended to create once, and then reuse the same map object to use them as strings, lists or tuples, etc.

Brief reproduction of the problem:

def concat(n):
  return n + "abc"
def upp(Lst):
  for i in Lst:
    if i[0].isupper():
      return i
def low(Lst):
  for i in Lst:
    if i[0].islower():
      return i

#main
L = ["a","B","c"]
m = map(concat,L) #Creating a Python map object
print(f"Capitalised string: {upp(list(m))} lowercased string: {low(list(m))}") #Accessing the returned manipulated map object

Expected Output:

Capitalised string: Babc lowercased string: aabc

Problem:

Actual output:

Capitalised string: Babc lowercased string: None

#Manual Debugging:
u = upp(list(m))
l = low(list(m))
print(u,l)

Output:

["aabc","Babc","cabc"][]

So as you can see, the second time I try to retrieve the map object, it doesn't return anything in the list.

Final Question:

I want to know why is it so that the map object is not accessible even when it does exist.

Note:

1. The following questions don't answer my question:

   • Map function not returning a value because:

     I. Not related to Python map object.

     II. There the map object does return some value but it isn't being used properly.

   • map function isnt returning the values because:

     I. Not related to Python

     II. The map function object does return some value there.

   • Python - Printing Map Object Issue because:

     I. Much related to my question but still has not proper/relevant references/citations to materials explaining the reason(s) of it being treated as a consumable object.

   • Python: casting map object to list makes map object empty? because:

     I. Not enough citations to documentations clearly stating the fact.

2. Edits which improve the sample program which reproduces the problem will be welcomed.