Problem of "for" loop in creating fibonacci series

Question

I was making a program for fibonacci series.

x=0
y=1
print (x)
print (y)
z = None
for z in range(1,100,x+y):
    z=x+y
    print(z)
    x = y
    y = z

The problem was that the output showed numbers more than 100. Here is a sample of the output

Why are there values greater than 100?

Note: this program was written in python 3.6

not sure about the question, but here's some observations: `range(1,100,x+y)` is same as `range(1,100)` since default `step` value is `1`... that means the loop will iterate `99` times and you have 2 print stmts before the loop.. so total 101 lines in output.. — Sundeep, Sep 03 '18 at 15:06
The step argument doesn't change throughout the for loop, so it will always step as one. — , Sep 03 '18 at 17:25

score 0 · Answer 1 · answered Sep 03 '18 at 15:20

The problem is that you run the loop 100 times rather than checking if the result is less than 100. The code is probably easier to read if you use a while loop rather than a for loop:

x=0
y=1
while True:
    fib = x + y
    if fib < 100:
        print (fib)
        x = y
        y = fib
    else:
        break

Stanley · Answer 2 · 2018-09-03T15:46:11.960

If you want it to stop at a given number you need an if statement, if not you it will run the fibonacci sequence 100 times

x=0
for number in range(1,100):
    x = number + x
    if x <= 100:
        print(x)
    else:
        break

Also you dont have to use step as it automatically increments by one for each loop

And the answer to your Q why are they more than hundred: because you run the fibonacci sequence 100 times, you dont stop it when it reaches 100.

Problem of "for" loop in creating fibonacci series

2 Answers2