Problema con le stringhe e le liste

a = """523434513243.....41234123423"""

b = []
for x in a:
   b.append(int(x))

print(sum(b))

Traceback (most recent call last):
 File "<pyshell#144>", line 2, in <module>
   c.append(int(x))
ValueError: invalid literal for int() with base 10: ' '

a = ()

>>> a = """3710728753.....75591789781264330331690"""
>>>
>>> b = []
>>> for x in a:
       b.append(int(x))

       
>>> print(sum(b))
22660