CODEWITHSUNDEEP
pythongeneratoryield
Maryam Mohebbi
Maryam Mohebbi

Reputation: 81

yield + generator in python in class

I am very new in Python and I wanna create a generator object that yields two lists for Fibonacci sequence. First list of number and second list of fibonacci. The function define in the class. Before it I define fibonacci function as below:

def fib(self, _n,) -> int:
        if _n == 0:
            return 0
        if _n == 1:
            return 1
        return self.fib(_n-1) + self.fib(_n-2)

I need to define def fib_seq(self, _n): function with yield and use gen() together.

I did it:

def fib_seq(self, _n):
        """
        - input: n=4
        - output: generator object that produces:
            ([0, 1, 2, 3, 4],
             [0, 1, 1, 2, 3])
        """
        for i in range(_n):
            nlist = gen(i)
            flist = gen(self.fib(i))

        yield ([nlist], [flist])

but I got below error in test part:

Traceback (most recent call last):
  File --- line 161, in <module> # this part is in test section
    n, fib = next(gen)      # trigger generator
             ^^^^^^^^^
  File ---, line 53, in fib_seq # this part is my code
    nlist = gen(i)
            ^^^^^^
TypeError: 'generator' object is not callable

Upvotes: 0

Views: 193

Answers (1)

Matt Pitkin
Matt Pitkin

Reputation: 6392

I'm not sure what the gen function you are using is, but you don't need to use it. You could do (removing self in this example to have standalone functions):

def fib(_n):
    if _n == 0:
        return 0
    if _n == 1:
        return 1
    return fib(_n-1) + fib(_n-2)

def fib_seq(n):
    for i in range(n + 1):
        nlist = list(range(i + 1))
        flist = [fib(j) for j in range(i + 1)]
    yield (nlist, flist)

# as fib_seq yields a generator you have to use it in, e.g., a for loop
for k in fib_seq(4):
    print(k)

([0, 1, 2, 3, 4], [0, 1, 1, 2, 3])

Note that the for loop in fib_seq is a bit superfluous as it stands. You could move the yield to within the loop, e.g.,

def fib_seq(n):
    for i in range(n + 1):
        nlist = list(range(i + 1))
        flist = [fib(j) for j in range(i + 1)]
        yield (nlist, flist)

which would give:

for k in fib_seq(4):
    print(k)

([0], [0])
([0, 1], [0, 1])
([0, 1, 2], [0, 1, 1])
([0, 1, 2, 3], [0, 1, 1, 2])
([0, 1, 2, 3, 4], [0, 1, 1, 2, 3])

or, if you only want one output, have:

def fib_seq(n):
    nlist = list(range(n + 1))
    flist = [fib(j) for j in range(n + 1)]
    yield (nlist, flist)

which would give:

for k in fib_seq(4):
    print(k)

([0, 1, 2, 3, 4], [0, 1, 1, 2, 3])

Upvotes: 1

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