if code returning none value while it should return a specified value

Question

Checked my loop several times. I cannot spot a mistake need another pair of eyes to help out. The code below is returning none while it should return a particular value.

I have checked the value of self.mdlname it is correct. I think there is something to do with with first function curr. It is not correctly reassigning value to self.currency. I see no other reason why it should return a none value.

Below ommitted functions after spartSABR function

import string

datatype = "Inflation SABR Vol ATM ZC"
dataconvention = "UK-RPI-ZERO-COUPON-SWAP-RATE"
mdlname = 'INFLATION_SABR'
t1 = 'should-send-back-none'


class srtqualifier:
    def __init__(self,mdlname,datatype, dataconvention,t1):
        self.mdlname = mdlname
        self.datatype = datatype
        self.dataconvention = dataconvention
        self.t1 = t1 ##TO BE REMOVED, ONLY USE FOR TESTING##
        self.tempholder =  self.dataconvention.split("-")
        self.currency = self.tempholder[0]

    def curr(self):
        if self.mdlname == 'INFLATION_SABR':
            inflationcurrency = {'UK':'GBP','FR':'EUR','EU':'EUR','US':'USD'}
            self.currency = inflationcurrency.get(self.currency)
            return self.currency

    def spartSABR(self):
        if self.dataconvention == 'JPY-SWAPTION-CLEAREDPHYSICAL-SEMI-ACT365F':
            return 'LIBOR_JPY_6M'
        elif self.dataconvention == 'USD-SIFMA Municipal Swap Index-1W-SWAPTION-PHYSICAL-SEMI-BOND':
            secondpartsp = self.tempholder[1].split(" ")
            secondpartsp.append(self.tempholder[2])
            separator = "_"
            secondpart = separator.join(secondpartsp[1:len(secondpartsp)])
            secondpart = secondpart.upper()
            return secondpart
        elif self.mdlname == 'INFLATION_SABR':
            secondpartsp = self.tempholder[0:2]
            secondpartsp = secondpartsp.append([self.currency,'1Y'])
            return secondpartsp
        else:
            secondpartsp = self.tempholder[1].split(" ")
            secondpartsp.append(self.tempholder[2])
            secondpartsp.insert(1,self.currency)
            separator = "_"
            secondpart = separator.join(secondpartsp)
            secondpart = secondpart.upper()
            return secondpart

test1 = srtqualifier(mdlname,datatype,dataconvention,t1)
print (test1.curr())
print (test1.spartSABR())

The `return` in `curr` is inside the `if` statement. Is that what you want? — Matthew Strawbridge, Apr 03 '19 at 14:16
This is wrong: ``secondpartsp = secondpartsp.append([self.currency,'1Y'])``. ``append`` returns ``None``, overwriting ``secondpartsp`` before it is returned. — MisterMiyagi, Apr 03 '19 at 14:21
Possible duplicate of https://stackoverflow.com/questions/16641119/why-does-append-return-none-in-this-code. — MisterMiyagi, Apr 03 '19 at 14:22
@MisterMiyagi it needs to be overwritten before it is returned — Varun Yadav, Apr 03 '19 at 14:37
@VarunYadav "it needs to be overwritten before it is returned" Why should that be the case? You can (and should) just return the original ``secondpartsp``. — MisterMiyagi, Apr 03 '19 at 14:53

score 0 · Answer 1 · answered Apr 03 '19 at 14:47

secondpartsp = secondpartsp.append([self.currency,'1Y']) this appends [self.currency,'1Y'] onto secondpartsp.But the append method doesn't return anything(it returns None),it doesn't return the list as you might be thinking.So then what happens is the result (None) gets assigned to secondpartsp, and now secondpartsp is empty.

import string

datatype = "Inflation SABR Vol ATM ZC"
dataconvention = "UK-RPI-ZERO-COUPON-SWAP-RATE"
mdlname = 'INFLATION_SABR'
t1 = 'should-send-back-none'


class srtqualifier:
    def __init__(self,mdlname,datatype, dataconvention,t1):
        self.mdlname = mdlname
        self.datatype = datatype
        self.dataconvention = dataconvention
        self.t1 = t1 ##TO BE REMOVED, ONLY USE FOR TESTING##
        self.tempholder =  self.dataconvention.split("-")
        self.currency = self.tempholder[0]

    def curr(self):
        if self.mdlname == 'INFLATION_SABR':
            inflationcurrency = {'UK':'GBP','FR':'EUR','EU':'EUR','US':'USD'}
            self.currency = inflationcurrency.get(self.currency)
            return self.currency

    def spartSABR(self):
        if self.dataconvention == 'JPY-SWAPTION-CLEAREDPHYSICAL-SEMI-ACT365F':
            return 'LIBOR_JPY_6M'
        elif self.dataconvention == 'USD-SIFMA Municipal Swap Index-1W-SWAPTION-PHYSICAL-SEMI-BOND':
            secondpartsp = self.tempholder[1].split(" ")
            secondpartsp.append(self.tempholder[2])
            separator = "_"
            secondpart = separator.join(secondpartsp[1:len(secondpartsp)])
            secondpart = secondpart.upper()
            return secondpart
        elif self.mdlname == 'INFLATION_SABR':
            secondpartsp = self.tempholder[0:2]
            secondpartsp.append([self.currency,'1Y'])
            return secondpartsp
        else:
            secondpartsp = self.tempholder[1].split(" ")
            secondpartsp.append(self.tempholder[2])
            secondpartsp.insert(1,self.currency)
            separator = "_"
            secondpart = separator.join(secondpartsp)
            secondpart = secondpart.upper()
            return secondpart

test1 = srtqualifier(mdlname,datatype,dataconvention,t1)
print (test1.curr())
print (test1.spartSABR())

score -1 · Accepted Answer · answered Apr 03 '19 at 15:04

Based on the logic provided by Ganga Siva Krishna. I figured out the problem. I didnt need to assign and append together. Solution is below:

def spartSABR(self):
        if self.dataconvention == 'JPY-SWAPTION-CLEAREDPHYSICAL-SEMI-ACT365F':
            return 'LIBOR_JPY_6M'
        elif self.dataconvention == 'USD-SIFMA Municipal Swap Index-1W-SWAPTION-PHYSICAL-SEMI-BOND':
            secondpartsp = self.tempholder[1].split(" ")
            secondpartsp.append(self.tempholder[2])
            separator = "_"
            secondpart = separator.join(secondpartsp[1:len(secondpartsp)])
            secondpart = secondpart.upper()
            return secondpart
        elif self.mdlname == 'INFLATION_SABR':
            secondpartsp = self.tempholder[0:2]
            print(self.tempholder[0:2])
            secondpartsp.append(self.currency)## I was doing secondpartsp= secondpartsp.append(self.currency)
            secondpartsp.append('1Y')
            separator = "_"
            secondpartsp = separator.join(secondpartsp)
            return secondpartsp
        else:
            secondpartsp = self.tempholder[1].split(" ")
            secondpartsp.append(self.tempholder[2])
            secondpartsp.insert(1,self.currency)
            separator = "_"
            secondpart = separator.join(secondpartsp)
            secondpart = secondpart.upper()
            return secondpart

if code returning none value while it should return a specified value

2 Answers2