Python Fibonacci generator using generators

Python: Generators Yield Exercise-4 with Solution

Write a Python program to implement a generator function that generates the Fibonacci sequence.

In mathematics, the Fibonacci sequence is a sequence in which each number is the sum of the two preceding ones. Numbers that are part of the Fibonacci sequence are known as Fibonacci numbers. Starting from 0 and 1, the first few values in the sequence are: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144.

Sample Solution:

Python Code:

def fibonacci():
    x, y = 0, 1
    while True:
        yield x
        x, y = y, x + y

# Accept input from the user
n = int(input("Input the number of Fibonacci numbers you want to generate? "))

print("Number of first ",n,"Fibonacci numbers:")
fib = fibonacci()
for _ in range(n):
    print(next(fib),end=" ")

Sample Output:

Input the number of Fibonacci numbers you want to generate? 4
Number of first  4 Fibonacci numbers:
0 1 1 2
Input the number of Fibonacci numbers you want to generate? 10
Number of first  10 Fibonacci numbers:
0 1 1 2 3 5 8 13 21 34


In the above exercise,

  • The fibonacci() function is defined as a generator function. It initializes two variables x and y with 0 and 1, respectively.
  • The function enters an infinite loop using while True.
  • Inside the loop, it uses the yield keyword to yield the current value of x. This represents the Fibonacci number in the sequence.
  • After yielding a, the function updates x and y by swapping their values: x becomes y, and y becomes the sum of the previous values of x and y.
  • The loop continues, generating the next Fibonacci number each time yield is encountered.
  • To use this generator and print the Fibonacci sequence, iterate over it using a loop. Use the next() function to manually retrieve the next Fibonacci number.


Flowchart: Python Fibonacci generator using generators

Python Code Editor:

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