Python calling method in class has no attribute/got an unexpected keyword argument-CodePudding

I am new to Python and I am trying to define a simple class with attributes and one method.

import scipy.optimize as optimize

class BondPricing:
    
    def __init__(self, price = 95.0428,par = 100,T = 1.5,freq = 2,coup_perc = 5.75,dy = 0.01,guess = 0.05):
        self.price = price
        self.par = par
        self.T = T
        self.freq = freq
        self.coup_perc = coup_perc
        self.dy = dy
        self.guess = guess
        
    def ytm(self):
        freq = float(self.freq) #cast frequency as float data type
        periods = self.T*freq #calculate number of cash flow periods
        coupon = self.coup_perc/100.*self.par/freq #calculate actual periodic coupon level
        dt = [(i 1)/freq for i in range(int(periods))] #calculate time steps in bond maturity
        #write down ytm function from bond pricing formula
        ytm_func = lambda y:sum([coupon/(1 y/self.freq)**(self.freq*t) for t in dt]) self.par/(1 y/self.freq)**(self.freq*self.T)-self.price
        return optimize.newton(ytm_func, self.guess) #find root of ytm function via Newton-Raphson 


bond1 = BondPricing()

When I try to call the method of the class with bond1.ytm(price = 95.0428, par = 100, T = 1.5, coup_perc = 5.75, freq = 2), I get the following error:

TypeError: ytm() got an unexpected keyword argument 'price'

or when I try:

bond1.ymt()

I get this error:

AttributeError: 'BondPricing' object has no attribute 'ymt'

Can anyone kindly explain me what am I doing wrong?

Many thanks in advance!

CodePudding user response：

When I try to call the method of the class with bond1.ytm(price = 95.0428, par = 100, T = 1.5, coup_perc = 5.75, freq = 2), I get the following error:

TypeError: ytm() got an unexpected keyword argument 'price'

The error is because the ytm method does not accept any arguments. You should be passing the arguments when you intialize the class. Example:

    bond1 = BondPricing(price = 95.0428, par = 100, T = 1.5, coup_perc = 5.75, freq = 2)
    # now call ytm method on the object
    bond1.ytm()

or when I try: bond1.ymt() I get this error:

AttributeError: 'BondPricing' object has no attribute 'ymt'

You have defined the method name as ytm. You should be calling it as

bond1.ytm() # not bond1.ymt()