Iterators? Python

Question

When i was looking for fibonaccis sequence code to compare to mine i found one answer i actually dont understand:

def F():
a,b = 0,1
while True:
yield a
a, b = b, a + b

especially the last line is totally strange.
Read that if language supports iterators you can make such code. What does it mean?

Answer 1

In Python you can write a, b = b, a which means that a and b switch their values.

If you wrote a = b and then b = a,
both a and b would end up with the same value.

In other languages you would need an extra line that keeps the in-between value, or a more complicated expression.

So when you have a number of names on the left side separated by commas and on the right side the same number of values (or expressions), they will be assigned simultaneously.

Answer 2

http://interactivepython.org/runestone/static/pip2/Tuples/TupleAssignmentwithunpacking.html