passing arguments to Python Class

Question

I have created one Python class to parse the text Input File in order to have a file in CSV format. Below is my class code:

import os
from os import listdir

class MyClass:
    def __init__(self, filename, colsList):
        self.filename=filename
        self.colsList=colsList

    def textcsvconverter(self,filename,colsList):
        import csv
        print("colsList:",colsList)
        self.cols=colsList
        outputfilename=(os.path.basename(filename))
        print("outputfilename:",outputfilename)
        fname_out =(outputfilename + '.csv')
        with open(filename) as fin, open(fname_out, 'wt') as fout:
            writer = csv.writer(fout, delimiter=",", lineterminator="\n")
            for line in fin:
                line = line.rstrip()  # removing the '\n' and other trailing whitespaces
                data = [line[c[0]:c[1]] for c in cols]
                writer.writerow(data)
            return fname_out

Now I have imported this class in my Pyspark code and trying to access the class method as shown below:

myobjectx = MyClass()
colsListA = [(0,1), (1,23), (23,31), (31,35),(35,41)]
outputfile1=myobjectx.textcsvconverter(finalpath1,colsListA)

Its giving me below error message:

TypeError: __init__() takes exactly 3 arguments (1 given)

Both filename and colsList are mandatory arguments. You should provide its values while instantiating the object . (ie, myobjectx = MyClass(your_filename, you_colsList) ) — user459872
– user459872, Commented Oct 16, 2018 at 6:00

Frank AK · Accepted Answer · 2018-10-16 07:29:14Z

1

You have declare your class with init method with 3 arguments. but you have input it. As you code show, you can get a default value in the init method.

def __init__(self, filename=None, colsList=[]):
    self.filename=filename
    self.colsList=colsList

So, that you can declare your instance without put any argument into it.

myobjectx = MyClass()

And, you can lazy assign or put argument in like you are doing with textcsvconverter method now.

UPDATE

As your comment below, I can see you are trying to make an instance of your class with a certain input :

finalpath1 = 'your-filename.csv' # I assume you have it
colsListA = [(0,1), (1,23), (23,31), (31,35),(35,41)] 
myobjectx = MyClass(finalpath1,colsListA)
outputfile1=myobjectx.textcsvconverter()

And you have to update your textcsvconverter to use your self.attribute.

edited Oct 16, 2018 at 7:29

answered Oct 16, 2018 at 5:58

Frank AK

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1 Comment

Vikrant Singh Rana Over a year ago

This is how I am calling my class now colsListA = [(0,1), (1,23), (23,31), (31,35),(35,41)] myobjectx = MyClass(finalpath1,colsListA) outputfile1=myobjectx.textcsvconverter() I am getting below error message self.colsList=cols NameError: global name 'cols' is not defined

Ankit Kumar Rathod · Accepted Answer · 2018-10-16 06:26:29Z

1

As per my knowledge, you took the two arguments in init method. that's the reason, you will get the error.

 TypeError: __init__() takes exactly 3 arguments (1 given)

The solution is, you should change your init method something like this.

def __init__(self, filename=None, colsList=[]):
    self.filename=filename
    self.colsList=colsList

OR

colsListA = [(0,1), (1,23), (23,31), (31,35),(35,41)]
myobjectx = MyClass(finalpath1, colsListA)
outputfile1=myobjectx.textcsvconverter(finalpath1,colsListA)

In the above second case, you need to modify your whole code.

import os
from os import listdir

class MyClass:
def __init__(self, filename, colsList):
    self.filename=filename
    self.colsList=colsList

def textcsvconverter(self):
    import csv
    print("colsList:",self.colsList)
    self.cols=self.colsList
    outputfilename=(os.path.basename(self.filename))
    print("outputfilename:",outputfilename)
    fname_out =(outputfilename + '.csv')
    with open(self.filename) as fin, open(fname_out, 'wt') as fout:
        writer = csv.writer(fout, delimiter=",", lineterminator="\n")
        for line in fin:
            line = line.rstrip()  # removing the '\n' and other trailing    whitespaces
            data = [line[c[0]:c[1]] for c in cols]
            writer.writerow(data)
        return fname_out


  colsListA = [(0,1), (1,23), (23,31), (31,35),(35,41)]
  myobjectx = MyClass(finalpath1,colsListA)
  outputfile1=myobjectx.textcsvconverter()

answered Oct 16, 2018 at 6:26

Ankit Kumar Rathod

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1 Comment

Vikrant Singh Rana Over a year ago

Thanks :-) I have made the changes as suggested. I am getting below error now: data = [line[c[0]:c[1]] for c in cols] NameError: global name 'cols' is not defined.. This is how I am calling through Pyspark colsListA = [(0,1), (1,23), (23,31), (31,35),(35,41)] myobjectx = MyClass(finalpath1,colsListA) outputfile1=myobjectx.textcsvconverter()

Vikrant Singh Rana · Accepted Answer · 2018-10-16 07:27:38Z

0

Its working now after a small change :-) cols=self.colsList Thanks all for your help and support

answered Oct 16, 2018 at 7:27

Vikrant Singh Rana

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