Can someone help me understanding this code please?-CodePudding

def fibonacci(n):
    if 0 <= n <= 1:
        return n

    n_minus1, n_minus2 = 1, 0
    result = None
    for f in range(n - 1):
       result = n_minus2   n_minus1
       n_minus2 = n_minus1
       n_minus1 = result

    return result

CodePudding user response：

Try using a couple of different numbers for n and see what results you get. You should be getting Fibonacci numbers.

CodePudding user response：

Thanks for asking the questions. This code is for basically for adding the series of fibonacci series.Taking n or number of element of series are argument.

def fibonacci(n):
    if 0 <= n <= 1:
        return n
    n_minus1, n_minus2 = 1, 0
    result = None
    for f in range(n - 1):
        result = n_minus2   n_minus1
        n_minus2 = n_minus1
        n_minus1 = result
    return result
print(fibonacci(1))

CodePudding user response：

def fibonacci(n):
    if 0 <= n <= 1:
        return n
    n_minus1, n_minus2 = 1, 0
    result = None
    for f in range(n - 1):
        result = n_minus2   n_minus1
        n_minus2 = n_minus1
        n_minus1 = result
    return result
print(fibonacci(1))

The Fibonacci Sequence is the series of numbers:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ...

The next number is found by adding up the two numbers before it:

the 2 is found by adding the two numbers before it (1 1),
the 3 is found by adding the two numbers before it (1 2),
the 5 is (2 3),
and so on!
if 0 <= n <= 1:
        return n
In the given function if the number given is between 0 and 1 then that number is returned
n_minus1, n_minus2 = 1, 0
First you have initialised the values for variables n_minus1=1,n_minus2=0
result = None
For avoiding the garbage values you have taken result=None
for f in range(n - 1):
       result = n_minus2   n_minus1
       n_minus2 = n_minus1
       n_minus1 = result
Here you have taken a loop for repating addition
 result=0 1=1
so result=0
then you have assigned n_minus1 value to n_minus2 that is 
n_minus2=1
and assigned result value to n_minus1 that is n_minus1=1
So our new values are n_minus1=1,n_minus2=1
and again result is calculated by result = n_minus2   n_minus1
So result=1 1=2
and
n_minus2=n_minus1=1
n_minus1=result=2
again our new values are 
n_minus2=1
n_minus1=2
again result is calculated and we will get new values for n_minus1,n_minus2 
the above process runs for n-1 times