Python Calculator Application

[nilamo]

def checkIfInt(possibleInt):
   try:
       val = int(possibleInt)
       return True
   except ValueError:
       return False

What about str.isdigit()?

def checkIfInt(possibleInt):
    return possibleInt.isdigit()

>>> checkIfInt("42")
True
>>> checkIfInt("k13")
False
>>> checkIfInt("8.4")
False

As snippsat pointed out, the operator module could make things much cleaner for you: https://docs.python.org/3/library/operator.html