Script for reformatting Meetup.com exports into Excel friendly formats (requires first converting from Excel to CSV).

meetup_date_reformatter.py

import pandas as pd
import numpy as np
from datetime import datetime
from argparse import ArgumentParser, Namespace

DATETIME_COLUMNS = [
    "Joined Group on",
    "Last visited group on",
    "Last Attended",
]

DATETIME_INPUT_FORMAT = "%B %d, %Y"

def parse_args() -> Namespace:
    parser = ArgumentParser(description='Reformat the dates in a CSV file')
    parser.add_argument("--datetime-input-format", help='', default=DATETIME_INPUT_FORMAT, type=str)
    parser.add_argument("csv_input_file", help='Path to CSV file', type=str)
    parser.add_argument("--datetime-columns", help='List of column names (headers) to reformat', nargs="*", type=str, default=DATETIME_COLUMNS)
    return parser.parse_args()

if __name__ == "__main__":
    args = parse_args()

    df = pd.read_csv(args.csv_input_file)

    def reformat_date(s: str) -> str:
        if pd.isnull(s):
            return s
        else:
            return datetime.strptime(s, args.datetime_input_format)

    for column in args.datetime_columns:
        df[column] = df[column].map(reformat_date)

    df.to_csv(args.csv_input_file.replace('.csv', '_reformatted.csv'))