how to write generate Fibonacci in python

Question

def fib(a, b, f):

fib must generate (using yield) the generalized Fibonacci sequence, a and b is first and second element. f is function to get the third element instead of a+b as normal Fibonacci sequence. Use take function(which show below) to test it.

my code is below

def fib(a, b, f):
    x = a
    y = b
    yield x
    x, y = y, f(x,y)
    fib(x,y,f)

I don't know what is wrong of my code, when I try to test it, it show "TypeError: 'generator' object is not subscriptable"

the test case is:

 take(5, fib(0, 1, lambda x, y: x - y))

It should out put:

[0, 1, -1, 2, -3]

and take function as i write is :

def take(n, iterable):
       x = []
    if n <= 0:
        return x
    else:
        for i in range (0,n):
            x.append(iterable[i])
        return x

Is take (...) Python function? More likely from Haskell ;) — Anzel
– Anzel, Commented Jan 27, 2015 at 22:31

augurar · Accepted Answer · 2015-01-27 23:02:31Z

2

The message means that generators do not support indexing, so iterable[i] fails. Instead, use the next() function to get the next item from the iterator.

def take(n, iterable):
    x = []
    if n > 0
        itr = iter(iterable)     # Convert the iterable to an iterator
        for _ in range(n):       # Repeat n times
            x.append(next(itr))  # Append the next item from the iterator
    return x

Also, your fib() function will not work. You should not recurse at the end of the function; instead write a loop that yields a value each iteration.

def fib(a, b, f):
    x = a
    y = b
    while True:
        yield x
        x, y = y, f(x,y)

edited Jan 27, 2015 at 23:02

answered Jan 27, 2015 at 22:34

augurar

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Comments

martineau · Accepted Answer · 2015-01-27 23:22:47Z

0

You can't index into the results coming from a generator function like fib(). This following avoids that by using zip() with a range() argument. zip() stops automatically when one of its arguments reaches then end.

def fib(a, b, f):
    x, y = a, b
    while True:
        yield x
        x, y = y, f(x, y)

def take(n, iterable):
    return [] if n <= 0 else [v for _, v in zip(range(n), iterable)]

print( take(5, fib(0, 1, lambda x, y: x-y)) )

Output:

[0, 1, -1, 2, -3]

answered Jan 27, 2015 at 23:22

martineau

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Comments

groenhen · Accepted Answer · 2020-05-16 07:38:56Z

0

Fibonacci simplest method you'll ever come across:

a , b =0 , 1

for n in range(100):#any number 
    print(a)
    a = a + b
    print (b)
    b = b + a

edited May 16, 2020 at 7:38

groenhen

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answered May 15, 2020 at 21:53

Rono

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Comments

Tushar Parmar · Accepted Answer · 2022-09-08 12:06:02Z

0

def fibo(n):
    if n == 0:
        return 0
    elif n == 1:
        return 1
    else:
        return fibo(n - 1) + fibo(n - 2)


n = int(input("enter the number: "))
for i in range(n):
    print(fibo(i))

edited Sep 8, 2022 at 12:06

answered Sep 8, 2022 at 12:05

Tushar Parmar

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1 Comment

Jeremy Caney Over a year ago

Remember that Stack Overflow isn't just intended to solve the immediate problem, but also to help future readers find solutions to similar problems, which requires understanding the underlying code. This is especially important for members of our community who are beginners, and not familiar with the syntax. Given that, can you edit your answer to include an explanation of what you're doing and why you believe it is the best approach?

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