Python-сообщество

 v =input()
if not v.isdigit():
    print('...')

 symbols = set(list(str(c) for c in range(10)) + ['+', '-', '.', 'e', 'E'])
nombre = input('Введите число:')
if [c for c in nombre if c not in symbols]:
    print('No entiendo!')

 set(list(str(c) for c in range(10))

 [str(c) for c in range(10)]

 {str(c) for c in range(10)}

 if [c for c in nombre if c not in symbols]

  [str(c) for c in range(10)]

 list(str(c) for c in range(10))

  5           0 LOAD_GLOBAL              0 (list)
              3 LOAD_CONST               1 (<code object <genexpr> at 0x0000000004D9CE40, file "<ipython-input-9-d30f08a50c2d>", line 5>)
              6 LOAD_CONST               2 ('constr.<locals>.<genexpr>')
              9 MAKE_FUNCTION            0
             12 LOAD_GLOBAL              1 (range)
             15 LOAD_FAST                0 (n)
             18 CALL_FUNCTION            1 (1 positional, 0 keyword pair)
             21 GET_ITER
             22 CALL_FUNCTION            1 (1 positional, 0 keyword pair)
             25 CALL_FUNCTION            1 (1 positional, 0 keyword pair)
             28 RETURN_VALUE