The earlier version of what is now https://github.com/simonw/csv-diff

readable_diff.py

import csv
from dictdiffer import diff


def load_trees(filepath):
    fp = csv.reader(open(filepath))
    headings = next(fp)
    rows = [dict(zip(headings, line)) for line in fp]
    return {r["TreeID"]: r for r in rows}


def compare(prev_trees, trees):
    # Have any rows been removed or added?
    removed = [id for id in prev_trees if id not in trees]
    added = [id for id in trees if id not in prev_trees]
    # How about changed?
    removed_or_added = set(removed) | set(added)
    potential_changes = [id for id in trees if id not in removed_or_added]
    changed = [id for id in potential_changes if trees[id] != prev_trees[id]]
    # Now generate the readable summary
    summary = []
    title = []
    if added:
        fragment = "{} tree{} added".format(len(added), "" if len(added) == 1 else "s")
        title.append(fragment)
        summary.append(fragment + "\n")
        for id in added:
            summary.append("  {}".format(repr(trees[id])))
        summary.append("")
    if removed:
        fragment = "{} tree{} removed".format(len(removed), "" if len(removed) == 1 else "s")
        title.append(fragment)
        summary.append(fragment + "\n")
        for id in removed:
            summary.append("  {}".format(repr(prev_trees[id])))
        summary.append("")
    if changed:
        fragment = "{} tree{} changed".format(len(changed), "" if len(changed) == 1 else "s")
        title.append(fragment)
        summary.append(
            fragment + '\n'
        )
        for id in changed:
            d = list(diff(prev_trees[id], trees[id]))
            summary.append("  Tree {}".format(id))
            for _, field, (prev_value, current_value) in d:
                summary.append(
                    '    {}: "{}" => "{}"'.format(field, prev_value, current_value)
                )
            summary.append("")
        summary.append("")
    return (", ".join(title) + "\n\n" + ("\n".join(summary))).strip()


if __name__ == "__main__":
    print(
        compare(
            load_trees("Street_Tree_List-old.csv"), load_trees("Street_Tree_List.csv")
        )
    )