Parsing RFC 822 timestamps

README.md

Comparison using the python date format spec to parse RFC-822 date strings vs using dateutil.

In [1]: from timeit import timeit 
   ...: from time_rfc_822 import parse_RFC_822_naive, parse_RFC_822_dateutil 
   ...: sample_date_string = 'Fri, 06 Mar 2020 14:22:22 GMT' 
   ...: %timeit parse_RFC_822_naive(sample_date_string) 
   ...: %timeit parse_RFC_822_dateutil(sample_date_string)                                                                                                                                                                                                                                
17.5 µs ± 805 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
154 µs ± 12.6 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)

python -m time_rfc_822
Naive:
17.657512107998627
Dateutil:
152.03899231600008

time_rfc_822.py

from datetime import datetime

import pytz
from dateutil import parser


def parse_RFC_822_naive(timestring: str) -> datetime:
    """Create a datetime from an RFC 822 timestamp string"""
    tz = pytz.timezone(timestring[-3:])
    return pytz.UTC.normalize(
        tz.localize(datetime.strptime(timestring, "%a, %d %b %Y %H:%M:%S %Z"))
    )


def parse_RFC_822_dateutil(timestring: str) -> datetime:
    """
    Create a datetime from an RFC 822 timestamp string using the dateutil parser.
    """
    return pytz.UTC.normalize(parser.parse(timestring))


if __name__ == "__main__":
    from timeit import timeit
    sample_date_string = "Fri, 06 Mar 2020 14:22:22 GMT"
    print("Naive:")
    print(timeit('parse_RFC_822_naive(sample_date_string)', globals=globals()))
    print("Dateutil:")
    print(timeit('parse_RFC_822_dateutil(sample_date_string)', globals=globals()))