Python return class object from own nested method

Question

I am trying to return a custom class object from a method A that calls a second method C. Both methods A and C are inside the same class called StreetList. My reason for having method C is that there's another method B which also will call C, so I don't want to repeat the code in C.

I want all the properties of the class to be accessible in Jinja HTML, hence the question.

Method C returns the StreetList class object correctly if I put in the correct parameter. But I am doing something wrong and if I call A, A does not return the class StreetList, but just a None object. The parameters and internal code of methods A, B and C are fine as far as I have tested, I have a syntax misunderstanding I think.

The class init method here:

class StreetList(object):
    def __init__(self, list_length, street, district, numrange=None, adoption=None, rdclass=None, length=None,
             road_no=None, has_tfl=None, tfl_rd=None, cross_boro=None, boro1=None, boro2=None,
             is_split=None, split=None):
    self.list_length = list_length
    self.street = street
    self.district = district
    self.numrange = numrange
    self.adoption = adoption
    self.rdclass = rdclass
    self.length = length
    self.road_no = road_no
    self.has_tfl = has_tfl
    self.tfl_rd = tfl_rd
    self.cross_boro = cross_boro
    self.boro1 = boro1
    self.boro2 = boro2
    self.is_split = is_split
    self.split = split

The method which calls this inside this class:

@classmethod
def populate_list(cls, st_list):
    ....
    return cls(list_length, street, district, numrange, adoption, rdclass, length, road_no, has_tfl, tfl_rd,
               cross_boro, boro1, boro2, is_split, split)

And the method A that calls the above method C:

@classmethod
def get_mainlist(cls, streetpart, name_or_num=""):
....
    return cls.populate_list(mainlist)

Tx any tips!