python def calc _default_ add(x, y, op )

Question

I got (SyntaxError: invalid syntax)
with this exercise :
Define the function calc_default_add() which, when given two numeric inputs and the string "add" or "sub" either adds or subtracts the two numbers appropriately. If the string is not provided as a third parameter, make the default operation add. If any other operation is provided as the third parameter, make sure you print the string"Valid operation: add, sub".

def calc_default_add(x, y, op):
if (op == "add" or op == None"):
print(x = y)
elf(op == "sub"):
print(x-y)
else:
print("Valid operations : add, sub")

This is what I did:

def calc_default_add(x, y, op=def calc_default_add(x, y, op="add"): # Here I got (SyntaxError: invalid syntax)

if op != "add" or op != "sub":
print("Valid operations: add, sub")
elif op == "add":
return int(x + y)
elif op == "sub":
return int(x - y)
else:
return Nonead

Answer 1

The function header should be like:
def calc_default_add(x, y, op='add'):

This way you can specify 3 parameters or if you specify only 2, then the third one is defaulted to 'add'.

Answer 2

Your major logic problem is in your line:

if op != "add" or op != "sub":

The problem is this; if someone inputs "add", it satisfies the '!= "sub"' section of your if statement, so it prints your "Valid operations..." string. You need to have

if op != "add" and op != "sub":

to stop this happening. Now it will only return True if the input is different to "add" *and* "sub".

Edit: I didn't read your question correctly and I jumped ahead a bit, sorry!

Answer 3

Thanks alot. I appreciate your help.