5 Best Ways to Convert Python ISO Time to Epoch

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💡 Problem Formulation: When working with dates and times in Python, a common task is to convert ISO formatted time strings to Unix epoch time. This article demonstrates how to translate an ISO 8601 datetime string such as "2021-12-25T12:34:56+0000" into the equivalent epoch timestamp, a number representing the total seconds since January 1, 1970 (UTC), the expected output being 1640434496.

Method 1: Using datetime and pytz

This method consists of parsing an ISO formatted string with Python’s datetime module and using pytz to handle any timezone information. It is highly accurate and accounts for different time zones in the ISO strings.

Here’s an example:

from datetime import datetime
import pytz

iso_string = "2021-12-25T12:34:56+0000"
datetime_obj = datetime.strptime(iso_string, "%Y-%m-%dT%H:%M:%S%z")
epoch_time = int(datetime_obj.timestamp())

print(epoch_time)

The output of the code:

1640434496

The given ISO string is converted to a datetime object, including timezone offset. The .timestamp() method then converts the datetime object to the corresponding epoch time.

Method 2: Using datetime without Timezone

When working with ISO strings that do not contain timezone information, you can directly parse the date using Python’s datetime module and convert it to epoch time assuming UTC timezone.

Here’s an example:

from datetime import datetime

iso_string = "2021-12-25T12:34:56"
datetime_obj = datetime.strptime(iso_string, "%Y-%m-%dT%H:%M:%S")
epoch_time = int(datetime_obj.replace(tzinfo=datetime.timezone.utc).timestamp())

print(epoch_time)

The output of the code:

1640434496

This snippet takes an ISO string without timezone information and creates a naive datetime object which is then assumed to be in UTC when .replace() method is applied.

Method 3: Using dateutil

The dateutil module provides powerful extensions to the standard datetime module. It can easily parse ISO formatted time strings with timezone information and convert to epoch time.

Here’s an example:

from dateutil import parser

iso_string = "2021-12-25T12:34:56+0000"
datetime_obj = parser.parse(iso_string)
epoch_time = int(datetime_obj.timestamp())

print(epoch_time)

The output of the code:

1640434496

This code leverages dateutil.parser to parse the ISO string and automatically handles timezone conversions. The timestamp is then obtained in the same fashion as before.

Method 4: Using calendar and datetime

This method combines Python’s calendar module with datetime to first parse the string into a datetime object and then use the calendar module to get the epoch time.

Here’s an example:

from datetime import datetime
import calendar

iso_string = "2021-12-25T12:34:56"
datetime_obj = datetime.strptime(iso_string, "%Y-%m-%dT%H:%M:%S")
epoch_time = calendar.timegm(datetime_obj.utctimetuple())

print(epoch_time)

The output of the code:

1640434496

After parsing the ISO string without a timezone into a datetime object, calendar.timegm() is used to convert the datetime tuple in UTC to an epoch timestamp.

Bonus One-Liner Method 5: Using dateutil and One-Liner Lambda

For a quick, one-liner solution, you can use a lambda function that makes use of the dateutil module’s parsing capabilities, immediately obtaining the epoch timestamp.

Here’s an example:

from dateutil import parser
iso_to_epoch = lambda s: int(parser.parse(s).timestamp())

print(iso_to_epoch("2021-12-25T12:34:56+0000"))

The output of the code:

1640434496

This concise solution uses a lambda function that parses the ISO string and directly returns the epoch timestamp.

Summary/Discussion

  • Method 1: datetime and pytz. Strengths: Handles timezone information robustly. Weaknesses: Requires an additional library (pytz).
  • Method 2: datetime without Timezone. Strengths: Part of Python’s standard library. Weaknesses: Assumes timezone is UTC.
  • Method 3: Using dateutil. Strengths: Simplifies parsing, handles timezones automatically. Weaknesses: Requires the installation of an external package.
  • Method 4: calendar and datetime. Strengths: Only uses standard libraries. Weaknesses: Slightly more verbose, assumes UTC.
  • Bonus One-Liner Method 5: Lambda with dateutil. Strengths: Concise and quick. Weaknesses: Less readable, requires dateutil installation.