[EMAIL PROTECTED] wrote:
> There is problaly a really simple answer to this, but why does this
> function print the correct result but return "None":
>
> def add(x, y):
> if x == 0:
> print y
> return y
> else:
> x -= 1
> y += 1
> add(x, y)
>
> print add(2, 4)
One of the best things to do when you don't understand how a function is
working is to geneously sprinkle the code with tracing print statements:
>>> def add(x, y):
params = (x, y)
print "Starting Function", params
if x == 0:
print "x is zero", params
print y
return y
print "After Return", params
else:
print "Non-zero x", params
x -= 1
y += 1
print "Updated x & y", params, '->', (x,y)
add(x, y)
print "Should I be here?", params
print "Falling off end.", params
>>> print add(2, 4)
Starting Function (2, 4)
Non-zero x (2, 4)
Updated x & y (2, 4) -> (1, 5)
Starting Function (1, 5)
Non-zero x (1, 5)
Updated x & y (1, 5) -> (0, 6)
Starting Function (0, 6)
x is zero (0, 6)
6
Should I be here? (1, 5)
Falling off end. (1, 5)
Should I be here? (2, 4)
Falling off end. (2, 4)
None
--
http://mail.python.org/mailman/listinfo/python-list
