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  • I want to print Fibonacci Series using lambda() function with map() or reduce() function in Python.

Note: I did search on SO, but could only find questions related to Printing nth Fibonacci number. e.g Fibonacci numbers, with an one-liner in Python 3?

Community
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Sahil kalra
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    This is stackoverflow, not code golf. – roippi May 04 '14 at 05:53
  • What is the problem in sharing a tricky situation, I faced with all. ? ... even SO recommends it read: http://blog.stackoverflow.com/2011/07/its-ok-to-ask-and-answer-your-own-questions/ – Sahil kalra May 04 '14 at 05:56
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    It's okay (and encouraged) to ask and answer your own *on-topic* questions. This is a **bad** question, any way you slice it. This site is about solving programming problems, not a competition to see who can produce a "one liner". – roippi May 04 '14 at 05:59
  • @roppi ..See the link of the question I provided in the text.. it was also similar but it did help other people.. – Sahil kalra May 04 '14 at 06:03

6 Answers6

8

I have the following working solutions:

A. Using lambda() + reduce():

 >>> fib = lambda n: reduce(lambda x, _: x+[x[-1]+x[-2]], range(n-2), [0, 1])
 >>> fib(10)
 >>> [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

Note: Not able to use x.append(x[-1]+x[-2]). Gives AttributeError (Don't know why)

B. Using lambda() + map(): (Have to use a variable for result)

 >>> result = [0,1]
 >>> fib = lambda n: map(lambda _: result.append(result[-1] + result[-2]), xrange(n-2))
 >>> fib(10)                          ## Ignore its output ##
 >>> result                           ## Stores the result ##
 >> [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
Sahil kalra
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    I see two problems with your lambda() + reduce() solution. The first is you avoid doing a *reduction* by ignoring the second `lambda()` argument and treat `reduce()` as a simple iterator . The second problem is that `fib(1)` and `fib(2)` produce the same result but they shouldn't. – cdlane Sep 11 '16 at 18:20
  • about your note, that is because `x.append(...)` return `None` because is a operation in place of list, while reduce expect your the function to return a value that is going to be used in the next iteration, for that you can do this `(x.append(...),x)[1]` – Copperfield Sep 11 '16 at 18:38
  • I see two problems with your lambda() + map() solution. The first is that it doesn't work in Python 3 as its extreme lazy evaluation doesn't fill out `result` until something consumes the result of `map()`. (E.g. try wrapping your `map()` in an `any()`) The second problem is that `fib(1)` and `fib(2)` produce the same result but they shouldn't. – cdlane Sep 11 '16 at 18:50
  • the solution to problem that _cdlane_ mention, is to add `[:n]` to the list `[0,1]` -> `[0,1][:n]` – Copperfield Sep 11 '16 at 19:53
  • @Copperfield `fib = lambda n: reduce(lambda x, _: x+[x[-1]+x[-2]], range(n-1), [0, 1])[:-1]` also works. – Gabe Mar 25 '22 at 05:10
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Fibonacci using reduce() and lambda()

from functools import reduce

def fibonacci(count):
    sequence = (0, 1)

    for _ in range(2, count):
        sequence += (reduce(lambda a, b: a + b, sequence[-2:]), )

    return sequence[:count]

print(fibonacci(10))

OUTPUT

(0, 1, 1, 2, 3, 5, 8, 13, 21, 34)

Fibonacci using map() and lambda()

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

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

    return sequence[:count]

print(fibonacci(10))

OUTPUT

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

Code Snippet:

fibonacci = lambda number: number if number <= 1 else fibonacci(number - 1) + fibonacci(number - 2);
listOfFibonacciNumbers = list(map(fibonacci, range(0, 20, 1)));
print(listOfFibonacciNumbers);

Output:

[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181]

In place of 20, you can give your number. I hope this helps:)

naveench
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yo can try this for Fibonacci using reduce() and lambda()

def Fib(count):
    first =[0,1]
    for i in range(0,count-2):
        first.append(reduce(lambda x,y : x+y,first[-2:]))

    print(first) 
Fib(10)

output

[0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
amir msbh
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Here's what might help you! Implemented using reduce() and lambda

from functools import reduce

fibonacci_seq = [0, 1]
n = 10

reduce(lambda a, b: len(fibonacci_seq) < n and (fibonacci_seq.append(a+b) or a+b), fibonacci_seq)

(fibonacci_seq.append(a+b) or a+b) : as the <any_list>.append(ele) returns None, I'm using it to append the next element in the series to the fibonacci_seq. oring it with a+b allows to return a+b as the result to the reduce() function to operate on it with the next element in the sequence.

len(fibonacci_seq) < n : The list stops growing once the len(list) reaches n.

OUTPUT

print(fibonacci_seq)

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

The above method returns the right sequence for n = 2 onwards.

dasaki
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try this code which prints the first 10 Fibonacci numbers using LAMBDA

fib = lambda n: n if n<=1 else fib(n-1)+fib(n-2)

for i in range(10):print(fib(i))

Vignan Nani
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    Hi and welcome to SO. Please edit your answer and format your code as code. Also some description would be nice, it's not "look how clever one liner I wrote" site. – rsm Mar 04 '18 at 20:54