Selective data saving to a file in Python

June 6, 2023

I am defining a Fibonacci sequence and saving the data to a file. However, I would like to save only the distinct sequence, not the repeating ones. For example, [0,1] should be saved only once and not three times. I present the current and expected outputs.

def fibonacci(n):
    sequence = [0, 1]  
    while len(sequence) < n:  
        next_number = sequence[-1] + sequence[-2]  
        sequence.append(next_number)  
    return sequence


n = 10
for i in range(0,n): 
    result = fibonacci(i)
    print(result)
    
    with open("Fibonacci.txt", 'a') as f: 
        f.writelines('\n') 
        f.write(str(result))
    print(result)

The current saved data is

[0, 1]
[0, 1]
[0, 1]
[0, 1, 1]
[0, 1, 1, 2]
[0, 1, 1, 2, 3]
[0, 1, 1, 2, 3, 5]
[0, 1, 1, 2, 3, 5, 8]
[0, 1, 1, 2, 3, 5, 8, 13]
[0, 1, 1, 2, 3, 5, 8, 13, 21]

The data I expect to save

[0, 1]
[0, 1, 1]
[0, 1, 1, 2]
[0, 1, 1, 2, 3]
[0, 1, 1, 2, 3, 5]
[0, 1, 1, 2, 3, 5, 8]
[0, 1, 1, 2, 3, 5, 8, 13]
[0, 1, 1, 2, 3, 5, 8, 13, 21]

>Solution :

Just add a new variable last_result that stores the previous iteration value and use an If to check it:

def fibonacci(n):
    sequence = [0, 1]  
    while len(sequence) < n:  
        next_number = sequence[-1] + sequence[-2]  
        sequence.append(next_number)  
    return sequence

last_result = None
n = 10
for i in range(0,n): 
    result = fibonacci(i)
    print(result)
    
    if result != last_result:
        last_result = result
        with open("Fibonacci.txt", 'a') as f: 
           f.writelines('\n') 
           f.write(str(result))
        print(result)