Python | Find fibonacci series upto n using lambda

The Fibonacci numbers are the numbers in the following integer sequence. 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, …….. In mathematical terms, the sequence Fn of Fibonacci numbers is defined by the recurrence relation

F_n = F_n-1 + F_n-2  with seed values   F₀ = 0 and F₁ = 1.

Find the series of fibonacci numbers using lambda function. Code #1 : By using lambda and reduce method

Python3

from functools import reduce

fib = lambda n: reduce(lambda x, _: x+[x[-1]+x[-2]],
                                 range(n-2), [0, 1])

print(fib(5))

Output:

[0, 1, 1, 2, 3]

Explanation : The list taking first two parameters is 0 and 1, and add like x[-1] i.e 0 and x[-2] i.e 1 and append to variable x. There is a type conversion to list and due to reduce() method, the same function calls and due to range function this time parameter changes, then add this to previous result and again store it to list.   Code #2 : By using lambda and map function

Python3

def fibonacci(count):
    fib_list = [0, 1]

    any(map(lambda _: fib_list.append(sum(fib_list[-2:])),
                                         range(2, count)))

    return fib_list[:count]

print(fibonacci(10))

Output:

[0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

Explanation : We are taking the list fib_list which already has 0 and 1. Then in the next iteration, this will be used as input and result of their sum will append to the list.

Time complexity: O(n), where n is the length of fib_list.
Auxiliary Space: O(n), where n is the length of fib_list.