how to sum to large string number in python

How to sum these two large strings, if I transform to FLOAT it loses the accuracy.

str1= '5.123654879542658'
str2= '8.777548795426584'

str(float(string1) + float(string2))

>Solution :

The decimal package is for high precision (28 places by default) maths:

>>> from decimal import Decimal
>>> str1= '5.123654879542658'
>>> str2= '8.777548795426584'
>>> Decimal(str1) + Decimal(str2)
Decimal('13.901203674969242')

Update: @KarlKnechtel seems to have found a close duplicate, oh well…