How do you convert a string in the format of
DD/MM/YY
to a
date
in Python?
To convert a string in the format of
DD/MM/YY
to a date in Python import the
datetime
library and use the
datetime.datetime.strptime(date_string, format_string)
function (yes, that is not a typo the
datetime
library has a
datetime
class and it contains the
strptime
function).
To make it easier to access the
strptime()
function it helps to import the
datetime
class when the
datetime
library is imported, like so:
from datetime import datetime
.
Here’s an example of a string in the format
DD/MM/YY
and how it can be converted to a date in Python using the REPL:
>>> from datetime import datetime
>>> d = "31/07/22"
>>> datetime.strptime(d, "%d/%m/%y")
datetime.datetime(2022, 7, 31, 0, 0)
As you can see from the above result the
strptime()
function takes the string to convert into a
datetime
object and according to the second parameter changes the string due to the syntax of day of the month
%d
, the month of the year
%m
and the abbreviated 2-digit year
%y
.
As the result is a
datetime
object you can further amend the code so that the result just returns a
date
object. Here’s how this would look in the REPL:
>>> from datetime import datetime
>>> d = "31/07/22"
>>> datetime.strptime(d, "%d/%m/%y").date()
datetime.date(2022, 7, 31)
As you can see from the above code the result outputs a
date
object instead of a
datetime
object which previously contained hour and minute of the day.
ValueError
When Using
strptime
If you do encounter a
ValueError
when trying to convert a string into a
date
object then check both parameters of the
strptime
separately. Check the string being inserted into the first parameter
is an actual date
and then check the format string represents the format of the string being inserted.
For example, the following examples produce an error:
>>> from datetime import datetime
>>> d = "31/06/22"
>>> datetime.strptime(d, "%d/%m/%y").date()
ValueError: day is out of range for month
The reason for the
ValueError
in the above code is due to the original input string representing a date that does
not
exist: 31st June 2022 is not found on the Julian calendar!
Here’s another
ValueError
, see if you can spot the problem:
>>> from datetime import datetime
>>> d = "31/07/22"
>>> datetime.strptime(d, "%m/%d/%y").date()
ValueError: time data '31/07/22' does not match format '%m/%d/%y'
As you can see from the above output the
ValueError
detail helps to show that the format doesn’t align well with the input, therefore look to change the
format_string
in the second parameter of the
strptime
function.
Summary
In this article I explained how to use the
strptime()
function in the
datetime
library to convert a string in the format of
DD/MM/YY
to a
date
object in Python. The function takes two parameters, the first being the string to be converted and the second being the format of the string. The
date
object output can then be used to perform calculations on now that the string has been successfully formatted.
If you do experience any
ValueErrors
using the function check both the value of the string being converted that it is a valid date and the format of the string that it matches the composition of the date inserted into the first parameter.
