Python Class with Self - Positional argument errors while calling the class

Question

I am having issues with self, I have written a class to make a data comparison of two datasets which I am feeding in as a csv - while trying to call this function, I am getting a TypeError.

Here is my class

import csv
import time
import pandas as pd


start_time = time.time()


class compare_files:
    def __init__(self, source, target):
        self.source = source
        self.target = target

    def compare_csv(self):

        source_file = open(self.source, "r", encoding="utf8")
        target_file = open(self.target, "r", encoding="utf8")

        csv_reader_source = csv.reader(source_file, delimiter=',')

        csv_reader_target = list(csv.reader(target_file, delimiter=','))

        columns = []
        all_mistakes = []
        target_line = 0
        for row_source in csv_reader_source:

            if target_line == 0:
                for i in row_source:
                    columns.append(i)
                target_line = 1
                continue

            row_target = csv_reader_target[target_line]

            target_line += 1

            mistakes = []
            if len(row_target) != len(row_target):
                if len(mistakes) == 0:
                    mistakes.append(row_source[0])
                mistakes.append('number of columns in this row mismatch')

            for i in range(len(row_source)):
                if row_source[i] != row_target[i]:
                    if len(mistakes) == 0:
                        mistakes.append(row_source[0])
                    mistakes.append(columns[i])
                    mistakes.append(row_source[i])
                    mistakes.append(row_target[i])
            if len(mistakes) > 0:
                all_mistakes.append(mistakes)

        return all_mistakes, round(time.time() - start_time, 2)




all_mistakes, time_taken = compare_files.compare_csv(
    "source.csv", "target.csv")

for i in all_mistakes:
    print(i)

print("Execution time took %s seconds" % (time_taken))

and here is the error, My compare function should accept source and target both, but when I calling compare function it seems it only accepts one argument.

~/Desktop » python3 compar2.py                                                                        
Traceback (most recent call last):
  File "compar2.py", line 70, in <module>
    all_mistakes, time_taken = compare_files.compare_csv(
TypeError: compare_csv() takes 1 positional argument but 2 were given

Answer 1

you defined the two parameters in the constructor so you have to call the constructor first like this

com_files = compare_files("source.csv", "target.csv")

then call the compare_csv method without the two parameters like this

all_mistakes, time_taken = com_files.compare_csv()