DateTime

You can specify a CLI parameter as a Python datetime.

Your function will receive a standard Python datetime object, and again, your editor will give you completion, etc.

from datetime import datetime

import typer


def main(birth: datetime):
    print(f"Interesting day to be born: {birth}")
    print(f"Birth hour: {birth.hour}")


if __name__ == "__main__":
    typer.run(main)

Typer will accept any string from the following formats:

• %Y-%m-%d
• %Y-%m-%dT%H:%M:%S
• %Y-%m-%d %H:%M:%S

Check it:

$ python main.py --help

Usage: main.py [OPTIONS] BIRTH:[%Y-%m-%d|%Y-%m-%dT%H:%M:%S|%Y-%m-%d %H:%M:%S]

Arguments:
  BIRTH:[%Y-%m-%d|%Y-%m-%dT%H:%M:%S|%Y-%m-%d %H:%M:%S][required]

Options:
  --help                Show this message and exit.

// Pass a datetime
$ python main.py 1956-01-31T10:00:00

Interesting day to be born: 1956-01-31 10:00:00
Birth hour: 10

// An invalid date
$ python main.py july-19-1989

Usage: main.py [OPTIONS] [%Y-%m-%d|%Y-%m-%dT%H:%M:%S|%Y-%m-%d%H:%M:%S]

Error: Invalid value for 'BIRTH:[%Y-%m-%d|%Y-%m-%dT%H:%M:%S|%Y-%m-%d %H:%M:%S]': 'july-19-1989' does not match the formats '%Y-%m-%d', '%Y-%m-%dT%H:%M:%S', '%Y-%m-%d %H:%M:%S'.

Custom date format

You can also customize the formats received for the datetime with the formats parameter.

formats receives a list of strings with the date formats that would be passed to datetime.strptime().

For example, let's imagine that you want to accept an ISO formatted datetime, but for some strange reason, you also want to accept a format with:

• first the month
• then the day
• then the year
• separated with "/"

...It's a crazy example, but let's say you also needed that strange format:

Python 3.7+Python 3.7+ non-Annotated

from datetime import datetime

import typer
from typing_extensions import Annotated


def main(
    launch_date: Annotated[
        datetime,
        typer.Argument(
            formats=["%Y-%m-%d", "%Y-%m-%dT%H:%M:%S", "%Y-%m-%d %H:%M:%S", "%m/%d/%Y"]
        ),
    ],
):
    print(f"Launch will be at: {launch_date}")


if __name__ == "__main__":
    typer.run(main)

Tip

Prefer to use the Annotated version if possible.

from datetime import datetime

import typer


def main(
    launch_date: datetime = typer.Argument(
        ..., formats=["%Y-%m-%d", "%Y-%m-%dT%H:%M:%S", "%Y-%m-%d %H:%M:%S", "%m/%d/%Y"]
    ),
):
    print(f"Launch will be at: {launch_date}")


if __name__ == "__main__":
    typer.run(main)

Tip

Notice the last string in formats: "%m/%d/%Y".

Check it:

// ISO dates work
$ python main.py 1969-10-29

Launch will be at: 1969-10-29 00:00:00

// But the strange custom format also works
$ python main.py 10/29/1969

Launch will be at: 1969-10-29 00:00:00