What is a "yield" statement in a function?
python
Solution
Using `yield` makes the function a generator. The generator will continue to yield the `a` variable on each loop, waiting until the generator's `next()` method is called to continue on to the next loop iteration.
Or, until you `return` or `StopIteration` is raised.
Slightly modified to show use of `StopIteration`:
>>> def fib():
... a = 0
... b = 1
... while True:
... yield a
... a = b
... b += a
... if a > 100:
... raise StopIteration
...
>>>
>>> for value in fib():
... print value
...
0
1
2
4
8
16
32
64
>>>
>>> # assign the resulting object to 'generator'
>>> generator = fib()
>>> generator.next()
0
>>> generator.next()
1
>>> for value in generator:
... print value
...
2
4
8
16
32
64
>>>
Problem
Possible Duplicate: The Python yield keyword explained Can someone explain to me what the yield statement actually does in this bit of code here: ``` def fibonacci(): a, b = 0, 1 while True: yield a a, b = b, a+b ``` for number in `fibonacci()`: # Use the generator as an iterator; print number What I understand so far is, we are defining a function `finonacci()`, with no parameters? inside the function we are defining `a` and `b` equal to 0 and 1, next, while this is true, we are yielding `a`. What is this actually doing? Furthermore, while yielding `a`? `a` is now equal to `b`, while `b` is now equal to `a + b`. Next question, for number in `fibonacci()`, does this mean for every number in the function or what? I'm equally stumped on what yield and 'for number' are actually doing. Obviously I am aware that it means for every number in `fibonacci()` print number. Am I actually defining number without knowing it? Thanks, sorry if I'm not clear. BTW, it's for project Euler, if I knew how to program well this would be a breeze but I'm trying to learn this on the fly.