A python script to diff the columns of CSV files that match in different directories

diff-dirs.py

#!/usr/bin/env python
from __future__ import print_function

import os
import os.path
import sys
from csv import DictReader

class DictDiffer(object):
    """
    Calculate the difference between two dictionaries as:
    (1) items added
    (2) items removed
    (3) keys same in both but changed values
    (4) keys same in both and unchanged values
    """
    def __init__(self, current_dict, past_dict):
        self.current_dict, self.past_dict = current_dict, past_dict
        self.current_keys, self.past_keys = [
            set(d.keys()) for d in (current_dict, past_dict)
        ]
        self.intersect = self.current_keys.intersection(self.past_keys)

    def added(self):
        return self.current_keys - self.intersect

    def removed(self):
        return self.past_keys - self.intersect

    def changed(self):
        return set(o for o in self.intersect
                   if self.past_dict[o] != self.current_dict[o])

    def unchanged(self):
        return set(o for o in self.intersect
                   if self.past_dict[o] == self.current_dict[o])


def rowdiff(row1, row2):
    dd = DictDiffer(row1, row2)
    return dd.changed()
    

def csvdiff(filename, dir1, dir2):
    filename1 = os.path.join(dir1, filename)
    filename2 = os.path.join(dir2, filename)
    csv1 = DictReader(open(filename1))
    csv2 = DictReader(open(filename2))
    print("-" * 30)
    print(filename)
    for i, (row1, row2) in enumerate(zip(csv1, csv2), start=1):
        diffs = rowdiff(row1, row2)
        if diffs:
            print("line {0}".format(i))
            for column in diffs:
                print("{0}:\n\t{1}\n\t{2}".format(column, row1[column], row2[column]))


def diff(dir1, dir2):
    dir1_files = os.listdir(dir1)
    dir2_files = os.listdir(dir2)
    common = set(dir1_files).intersection(set(dir2_files))
    for filename in common:
        csvdiff(filename, dir1, dir2)

if __name__ == '__main__':
    dir1 = sys.argv[1]
    dir2 = sys.argv[2]
    diff(dir1, dir2)