python simple function error?

I have a simple function to do simple math operations. If I call this from another script using import, I get no output. If I remove def function, everything is working fine. What's the problem with defining this开发者_如何学Python function? I'm new to Python.

def calci(a, op, b): 
    if op == '+':
        c = a + b
    elif op == '-':
        c = a-b
    elif op == '*':
        c= a*b
    elif op =='/':
        if(b == 0):
            print('can\'t divide') 
            c = a/b
            print('value is',c)
            return c 
result  = calci(12,'+', 12)
print(result)

Do you want to return the result to the calling function or print it? The only path through your program that results in a return is division, and when you do this you'll never reach the print statement.

If you want to do both, you should dedent the part:

print('value is',c)
return c

...to the level of the if and elif statements. Don't forget to remove your testing code (result = calci(...) etc).

The reason is that once your code hits a return statement, that's it for the function — nothing else in it will be executed (not quite true, there is an exception handling mechanism called a finally block which is an exception to this, but that's not an issue here).

Added: since you want to just print it, remove the return statement and dedent the print statement.

Your indentation at the end of the function appears to be wrong; the print and return c are only happening if op == '/', and you're only assigning to c if b == 0. The end should be:

elif op =='/':
    if(b == 0):
        print('can\'t divide') # You should probably return here instead of falling through to the assignment

    c = a/b


print('value is',c)
return c

Your function only returns if op=='/'.

Remove a couple of tabs from those two lines and it'll work.

i.e.

def calci(a, op, b): 

    ...

    print('value is',c)
    return c

The indentation of the return part is incorrect, it should be lower-one-level. (This is so hard to describe... a flaw of Python's indentation syntax)

Here is the correct code:

def calci(a, op, b): 

    if op == '+':
        c = a + b

    elif op == '-':
        c = a-b

    elif op == '*':
        c= a*b

    elif op =='/':
        if(b == 0):
            print('can\'t divide')
            return 0

        c = a/b


    print('value is',c)
    return c

result  = calci(12,'+', 12)

print(result)