Given a string of words and numbers. Extract the expression including: 
1. the operator: either addition or subtraction
2. the two numbers that we are operating on
Return the result of the calculation.
Example:
"Panda has 48 apples and loses 4" returns 44
"Jerry has 34 apples and gains 6" returns 40
"loses" and "gains" are the only two words describing operators.
Should be a nice little kata for you :)
Note:
No fruit debts nor bitten apples = The numbers are integers and no negatives
from re import findall

def calculate(s):
    op1, op2 = map(int, findall('(\d+)', s))
    return op1 + op2 if 'gains' in s else op1 - op2
from re import findall

def calculate(s):
    op1, op2 = map(int, findall('(\d+)', s))
    return op1 + op2 if 'gains' in s else op1 - op2