Missing 2 required positional arguments - Classmethod Python

Question

Sorry, I'm struggling at this for quite some time. I'm trying to use function totalPayments which uses the monthlyPayment class function with parameters pass through in the initialisation phase. I'm getting an error missing 2 required positional arguments

class Loan(object):
   def __init__(self, asset, face, rate , term):
       self._asset = asset
       self._face = face
       self._rate = rate
       self._term = term

   @classmethod
   def monthlyPayment(cls,face,rate,term,period=None):
       return ((rate*face*((1+rate)**term)))/(((1+rate)**term)-1)

   def totalPayments(self):
       return (self.monthlyPayment(self) * self._term) 

l = Loan(None,1000,0.025,10)
print(l.totalPayments()) # gets an error missing 2 required positional arguments

edit: Thank you very much for the hekp and I should be amending my def monthlyPayment function to take in the arguments

You are only passing one parameter to a function that you defined to require three. Please clarify in how far the error is unexpected and/or unclear to you. — MisterMiyagi
– MisterMiyagi, Commented Dec 14, 2019 at 12:06
Note that it is entirely unclear why you defined the method as a classmethod in the first place - it does not use the class, it takes all fields of a class instance, and you pass it a class instance. — MisterMiyagi
– MisterMiyagi, Commented Dec 14, 2019 at 12:09

L3viathan · Accepted Answer · 2019-12-14 12:04:48Z

3

You are calling monthlyPayment from the instance (self), and you're not providing arguments for face, rate, and term.

It also shouldn't be a classmethod, since you use attributes of the instance:

class Loan(object):
   def __init__(self, asset, face, rate , term):
       self._asset = asset
       self._face = face
       self._rate = rate
       self._term = term

   def monthlyPayment(self, period=None):
       return ((self._rate*self._face*((1+self._rate)**self._term)))/(((1+self._rate)**self._term)-1)

   def totalPayments(self):
       return (self.monthlyPayment() * self._term)

answered Dec 14, 2019 at 12:04

L3viathan

27.5k2 gold badges63 silver badges84 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

L3viathan · Accepted Answer · 2019-12-14 12:06:15Z

The stack error you get is:

Traceback (most recent call last):
  File "C:/Users/cd00119621/PycharmProjects/ideas/stackoverflow.py", line 16, in <module>
    print(l.totalPayments())
  File "C:/Users/cd00119621/PycharmProjects/ideas/stackoverflow.py", line 13, in totalPayments
    return (self.monthlyPayment(self) * self._term)
TypeError: monthlyPayment() missing 2 required positional arguments: 'rate' and 'term'

The clue here is that its the monthlyPayment() method thats giving the error missing 2 args. this method expects 3 args passed to it (excluding self) and the 4th is optional.

def monthlyPayment(cls,face,rate,term,period=None):

but when you call this from your totalPayments method you only pass one argument which is self.

return (self.monthlyPayment(self) * self._term)

you dont need to pass self, it will be passed automatically, so you need to pass the other 3 expected params face,rate,term

Collectives™ on Stack Overflow

Missing 2 required positional arguments - Classmethod Python

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related