square root of a number greater than 10 2000 in Python 3

Question

I'd like to calculate the square root of a number bigger than 10^2000 in Python. If I treat this number like a normal integer, I will always get this result back:

Traceback (most recent call last):
  File "...", line 3, in <module>
    print( q*(0.5)  )
OverflowError: int too large to convert to float

How do I fix this? Or does a possibilty other than using Python exist to calculate this square root?