Conversion Between String & Datetime in Python

There are many different formats of writing dates or times, for dates alone there are common formats such as 18 Jul 2022, 2022–07–18, 18/07/22. Same goes for time representations including 4:45:00 pm, 16:45 and so on. In Python there is a built-in library for representation of datetime, using which you can perform comparison or arithmetic operations (addition and deletion) on different datetimes.

This article is gonna introduce how to convert from datetime to strings and vice versa using built-in methods in datetime library.

Converting Datetime to Strings

As an example, let’s get the current date and time using the now() function in datetime class under datetime library.

from datetime import datetime

now = datetime.now() # current date and time

now
>>> datetime.datetime(2022, 7, 18, 16, 50, 24, 470847)

The returned result is a datetime object consisting of the current year, month, day, followed by hour, minute, second and microsecond. You are able to get the different attribute by direct access as follows:

print(f"date: {now.date}")
print(f"year: {now.year}")
print(f"month: {now.month}")
print(f"day: {now.day}")
print(f"time: {now.time}")
print(f"hour: {now.hour}")
print(f"minute: {now.minute}")
print(f"second: {now.second}")
print(f"microsecond: {now.microsecond}")

>>> date: <built-in method date of datetime.datetime object at 0x00000222767FADB0>
>>> year: 2022
>>> month: 7
>>> day: 18
>>> time: <built-in method time of datetime.datetime object at 0x00000222767FADB0>
>>> hour: 16
>>> minute: 50
>>> second: 24
>>> microsecond: 545047

Now, to convert the datetime objects to different string format using method .strftime(format) :

Example 1: DD/MM/YYYY, HH:MM:SS

Example 2: DD MMM, YYYY for the date part

Here I am using %b for the abbreviated (3-letter) month name.

Example 3: Full name of the month, and time on 12-hour clock with AM/PM

Change %b to %B for the full month. For the time representation, %H is the hour number for 24-hour clock, and %I for 12-hour clock, both with zero padding, so it prints “04:50:24” instead of “4:50:24”.

Example 4: Month and Hour without Zero Padding

There are a lot more options that covered in the examples above, the full format code list as follows:

Text version for easier copy & paste:

Important note:

For the representations without zero padding, Windows has the code prefixed by “#”, however if you are using Linux, remember to replace “#” by “-”, so for example, the corresponding format for time string “8:9:3” in Windows is “%#H:%#M:%#S” but for Linux is “%-H:%-M:%-S”.

Converting Strings to Datetime

The conversion from strings to datetime works exactly the opposite as the other way round. Using strptime() method under datetime class, with a specific string and its format representation, you are able to get the equivalent datetime object.

Syntax: datetime.strptime(date_string, format) , format follows the same representations as the code list above, such as “%d/%m/%Y, %H:%M:%S”.

Example:

from datetime import datetime

print(datetime.strptime("18/07/2022, 16:50:24", "%d/%m/%Y, %H:%M:%S"))

>>> 2022-07-18 16:50:24

print(datetime.strptime("18 Jul, 2022, 16:50:24", "%d %b, %Y, %H:%M:%S"))

>>> 2022-07-18 16:50:24

print(datetime.strptime("18/7/22, 4:56:33.635 PM", "%d/%m/%y, %H:%M:%S.%f %p"))

>>> 2022-07-18 04:56:33.635000

Note that if the provided string and format do not match, the program will throw a ValueError:

print(datetime.strptime("18/07/2022", "%d/%m/%y"))

>>> ValueError: unconverted data remains: 22

Here the year 2022 should be matched against the code %Y instead of %y.

Datetime Object Operations

After the conversion from string to datetime, you are able to increment/decrement the object, or compute the difference between two datetime objects:

Increment/Decrement

dt1 = datetime.strptime("18/07/2022, 16:50:24", "%d/%m/%Y, %H:%M:%S")

from datetime import timedelta

# increment by 1 hour and 5 minutes
dt1 + timedelta(hours=1, minutes=5)

>>> datetime.datetime(2022, 7, 18, 17, 55, 24)

# decrement by 2 days 12 hours and 30 seconds
dt1 - timedelta(days=2, hours=12, seconds=30)

datetime.datetime(2022, 7, 16, 4, 49, 54)

Time Difference

dt1 = datetime.strptime("18/07/2022, 16:50:24", "%d/%m/%Y, %H:%M:%S")
dt2 = datetime.strptime("19/07/2022, 10:36:17", "%d/%m/%Y, %H:%M:%S")

# time difference
dt2 - dt1
>>> datetime.timedelta(seconds=63953)

dt1 - dt2
>>> datetime.timedelta(days=-1, seconds=22447)

# get number of seconds between dt1 and dt2
(dt2 - dt1).seconds
>>> 63953

# convert to minute
print(f"Time difference: {(dt2 - dt1).seconds / 60.0} minutes")
>>> Time difference: 1065.8833333333334 minutes

Thanks for reading! For more of my articles on Python & Cryptos, please refer to:

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