Convert IP address data in csv to CIDR format

convert_IP_to_CIDR.py

"""
Change IP to CIDR (ignore second IP) and export to CSV

Usage:
    python3 main.py <source_file>

Example data:
    <source_file>:
        1.0.174.0,1.0.174.255,AS,TH,"Nakhon Si Thammarat","Phra Phrom",8.33911,99.9009
        1.0.78.0,1.0.78.255,AS,JP,Hiroshima,Hiroshima,34.4002,132.475
        23.251.37.48,23.251.38.7,AS,CN,Shaanxi,Xi'an,34.3416,108.94

    <export_file>:
        16821760,AS,TH,"Nakhon Si Thammarat","Phra Phrom",8.33911,99.9009
        16797184,AS,JP,Hiroshima,Hiroshima,34.4002,132.475
        402335024,AS,CN,Shaanxi,Xi'an,34.3416,108.94
"""

import csv
import time
import sys
from pathlib import Path

SOURCE_FILEPATH = Path(sys.argv[1])
EXPORT_FILEPATH = SOURCE_FILEPATH.parent / "export.csv"


def read_data(filename, skip_header=False):
    with open(filename) as csv_file:
        if skip_header:
            next(csv_file)
        for row in csv_file:
            try:
                items = row.split(",")
                # items[-1] = items[-1].strip()
                yield items
            except ValueError:
                print(f"Failed to read {row[0]}")


def convertToCIDR(ip_address):
    nums = ip_address.split(".")
    result = int(nums[0]) * 16777216 + int(nums[1]) * 65536 + int(nums[2]) * 256 + int(nums[3])
    return result


def main():
    start = time.time()

    with open(EXPORT_FILEPATH, "w") as f:
        writer = csv.writer(f, delimiter=",", lineterminator="", quotechar="", quoting=csv.QUOTE_NONE)

        generator = read_data(SOURCE_FILEPATH)
        for ip1, _, *rest in generator:
            cidr = convertToCIDR(ip1)
            writer.writerow([cidr, *rest])
    end = time.time() - start

    print(f"Exported {EXPORT_FILEPATH.absolute()}")
    print(f"Done in {end:.2} seconds")


if __name__ == "__main__":
    main()