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PYTHON - FIBONACCI SERIES

A Fibonacci Series is generated by by adding the previous number of the sequence with the current number to generate the next number in the sequence.

Let us see the first six numbers of the Fibonacci Series.

0 1 1 2 3 5

Fibonacci Series using Iteration

Let us look at the below example to print first 6 numbers in the Fibonacci Series.

Example :

previous = 0
current = 1
print(previous)
print(current)
for i in range(4):
    temp = current
    current = previous + current
    previous = temp
    print(current)

Output :

0
1
1
2
3
5

So, in the above code, we have initialised the variables 'previous' and 'current' with '0' and '1' as those are the first two elements by default.

And we have printed '0' and '1' initially.

print(previous)
print(current)

Output :

0
1

So, we have printed the first two elements of the Fibonacci Series. And to print the rest 4 elements of the Fibonacci Series, we get into the 'for' loop.

for i in range(4):
    temp = current
    current = previous + current
    previous = temp
    print(current)

Let us see the Iterations of the 'for' loop.

1st Iteration

In the first Iteration, we have stored the 'current' value (i.e. '1') in a temporary variable 'temp'.

Then we add the 'current' and 'previous' value.

current = previous + current

And the new value of 'current' becomes '1 + 0 = 1',

Then in the next line, we take the value of 'temp' and put in 'previous'.

previous = temp

And the print statement inside the loop prints the value of 'current'(i.e. The next value of the sequence, '1').

Output :

0
1
1

Then starts the second Iteration.

2nd Iteration

Similarly, in the second Iteration, we have stored the 'current' value (i.e. '1' again) in the temporary variable 'temp'.

Then we add the 'current' and 'previous' value.

current = previous + current

And the new value of 'current' becomes '1 + 1 = 2',

Then in the next line, we take the value of 'temp' and put in 'previous'.

previous = temp

And the print statement inside the loop prints the value of 'current'(i.e. The next value of the sequence, '2').

Output :

0
1
1
2

3rd Iteration

Similarly, in the third Iteration, we have stored the 'current' value (i.e. '2') in the temporary variable 'temp'.

Then we add the 'current' and 'previous' value.

current = previous + current

And the new value of 'current' becomes '1 + 2 = 3',

Then in the next line, we take the value of 'temp' and put in 'previous'.

previous = temp

And the print statement inside the loop prints the value of 'current'(i.e. The next value of the sequence, '3').

Output :

0
1
1
2
3

4th Iteration

Similarly, in the fourth Iteration, we have stored the 'current' value (i.e. '3') in the temporary variable 'temp'.

Then we add the 'current' and 'previous' value.

current = previous + current

And the new value of 'current' becomes '3 + 2 = 5',

Then in the next line, we take the value of 'temp' and put in 'previous'.

previous = temp

And the print statement inside the loop prints the value of 'current'(i.e. The next value of the sequence, '5').

Output :

0
1
1
2
3
5

And we are done printing all the six values in the Fibonacci Sequence.

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