Learn how to format dates/times with f-strings and %-format specifiers.

Lately, I have tweeted a lot about dates and times.

In Python 🐍, the built-in module to work with those is datetime.

If you have a datetime object, you can format it easily with f-strings!

You just need to use the syntax you are used to:

>>> import datetime as dt
>>> now = dt.datetime.now()
>>> now
datetime.datetime(2022, 3, 17, 10, 42, 44, 770965)
>>> f"Today is the {now:%d-%m-%Y}."
'Today is the 17-03-2022.'

However, keep this in mind:

What you write on the right of the : inside the curly braces {} can be any string whatsoever!

It can be any string, and the % format specifiers will be replaced.

So, I can take the example above and turn the f-string inside out:

>>> f"{now:Today is the %d-%m-%Y.}" 
'Today is the 17-03-2022.'

That looks a bit funky, doesn't it? 🤪

It works, but it's not the recommended way of using the formatting.

Here are some more examples of specifiers that you can find cool/useful:

>>> import datetime as dt
>>> now = dt.datetime.now()
>>> now
datetime.datetime(2022, 3, 17, 11, 7, 20, 770789)

# Day of week name (%A) and month name (%B):
>>> f"Today is a fine {now:%A} of {now:%B}."
'Today is a fine Thursday of March.'
# Day of the year as a number 1 - 366 (%j):
>>> f"{now:%d/%m} is day number {now:%j} of the year {now:%Y}."
'17/03 is day number 076 of the year 2022.'
# Locale's appropriate date and time representation (%c):
>>> f"{now:%c}"
'Thu Mar 17 11:07:20 2022'

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