from random import randint
numbers = []
a = 0
while a < 10:
    a += 1
    numbers.append(a)
letters_set = 'ABCDE'
letters = []
for letter in letters_set:
    letters += letter
range_of_choice = numbers + letters #Если преобразовать в строку оба листа в этом месте, то всё равно ошибка
print('Диапазон выбора: ' + str(range_of_choice)) # str(range_of_choice) если тут перевести в строку, то будет нормально
print('Всего символов в диапазоне: ' + str(len(range_of_choice)))
def random_choice():
    pulled_number = randint(range_of_choice[0], len(range_of_choice))
    return pulled_number
print("Winning ticket is", end=': ')
winning_numbers = []
for a in range(6):
    if winning_numbers not in winning_numbers:
        winning_numbers.append(random_choice())
print(winning_numbers)

[code python]сюда вставить код[/code]

 print('Диапазон выбора: ' + str(range_of_choice)) # str(range_of_choice) если тут перевести в строку, то будет нормально

  print('Диапазон выбора: ' + "".join(range_of_choice))

  
letters_set = 'ABCDE'
letters = []
for letter in letters_set:
    letters += letter

  
>>> letters_set = 'ABCDE'
>>> letters = []
>>> for letter in letters_set:
...     letters += letter
... 
>>> 
>>> letters_set = 'ABCDE'
>>> letters = []
>>> for letter in letters_set:
...     letters = letters + letter
... 
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
TypeError: can only concatenate list (not "str") to list
>>>

  
>>> lst = [123]
>>> 
>>> for i in 1, 2, 3:
...   lst += i
... 
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
TypeError: 'int' object is not iterable
>>>

  
>>> 'abc' + [123]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: must be str, not list
>>> 

  
>>> [123] + 'abc'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: can only concatenate list (not "str") to list
>>>

  
>>> range_of_choice = ['a', 'b', 'c']
>>> 
>>> range_of_choice
['a', 'b', 'c']
>>> 
>>> print('Диапазон выбора:', range_of_choice)
Диапазон выбора: ['a', 'b', 'c']
>>>

  
>>> range_of_choice = ['a', 'b', 'c']
>>> 
>>> range_of_choice
['a', 'b', 'c']
>>> 
>>> print('Диапазон выбора:', *range_of_choice)
Диапазон выбора: a b c
>>>