Question

I copied the source code of a python program written by someone else on a tutorial forum and I have made a few modifications to it to match my own needs

the original was meant to run in the python shell i believe and i got it to run in the shell but I need to save it to python IDLE and run it from there

I am using python 3.2.3 IDLE btw
this is what I have written:

def fibonacci(previous=0,current=1):
    n = int(input("Calculate fibonacci sequence value up to: "))
    if previous > current:
        previous,current = current, previous
    yield previous
    yield current
    while True:
        current,previous = previous+current,current
        yield current

    x = fibonacci()    
    for i in range(n):
        print(next(x))
fibonacci()

it doesn’t run, like no errors pop up i just get the arrows: >>
that’s it nothing happens.

Answer 1

The program does start and runs through. Unfortunately, by using yield in the function, you make it a generator, and the generator gets only constructed in the last line, but never evaluated.

Instead, you want to outdent the last four lines:

def fibonacci(previous=0,current=1):
    if previous > current:
        previous,current = current, previous
    yield previous
    yield current
    while True:
        current,previous = previous+current,current
        yield current

n = int(input("Calculate fibonacci sequence value up to: "))
x = fibonacci()    
for i in range(n):
    print(next(x))