participant_list = ['A', 'B', 'C']
receiver_list = copy(participant_list)

for participant in participant_list:

    possible_receivers = receiver_list.remove(participant) 
    # remove the participant from the list so that our participant could not match with themselves

    match = choice(possible_receivers) 
    # select a random participant as our match using python's random.choice

    receiver_list.remove(match) 
    # remove that participant from the list as they've already found a secret santa 😉-🎅

>>> people_pool = ['A', 'B', 'C']
>>> people_pool
['A', 'B', 'C']
>>> receiver_pool = people_pool[::-1] # shallow copy
>>> receiver_pool
['A', 'B', 'C']
>>> for person in people_pool:
...     possible_receivers = receiver_pool.remove(person)
...     match = choice(possible_receivers)
...     receiver_pool.remove(match)

# runs

# 1
person  # A
possible_receivers  # ['A', 'B', 'C'] -> remove self from receiver list -> ['B', 'C']
match  # ['B', 'C'] -> 'B' is chosen 
receiver_pool  # ['A', 'B', 'C'] -> remove choice from receiver list -> ['A', 'C']

# 2
person  # B
possible_receivers  # ['A', 'C'] -> remove self from receiver list (we are not in it) -> ['A', 'C'] 
match  # ['A', 'C'] -> 'A' is chosen 
receiver_pool  # ['A', 'C'] -> remove choice from receiver list -> ['C']

# 3
person  # C
possible_receivers  # ['C'] -> we are the only possible receiver, since: A => B; B => A -> we remove ourself from the pool -> []
match  # [] -> the list is empty and we cannot make a match 
receiver_pool  # [] -> we have no match, and probably error out of range index