How to Solve Python ValueError: unconverted data remains

If you want to format a datetime using datetime.strptime(), the format needs to match the original string. If there is a mismatch between the format and the original string, strptime will not be able to parse the string and will raise the ValueError: unconverted data remains.

To solve this error, ensure that the format you are using matches the string you want to parse.

This tutorial will go through the error in detail and how to solve it with code examples.

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Python ValueError: unconverted data remains

In Python, a value is a piece of information stored within a particular object. We will encounter a ValueError in Python when using a built-in operation or function that receives an argument that is the right type but an inappropriate value. In this specific error, the data we pass to the datetime.strptime() method is the correct type, string, but has an incorrect format.

The strptime method is available in the DateTime module and formats a timestamp in string format to a datetime object. The syntax of the method is as follows:

datetime.strptime(date_string, format)

Parameters

• date_string: Required. String to convert to datetime object.
• format: Required. Format code

Returns

The method returns a datetime object corresponding to date_string, parsed according to format.

ValueError is raised if time.strptime() cannot parse date_string and format.

Example

Let’s look at an example where we want to convert a string representing a string to a datetime object.

from datetime import datetime

# Define date string

date_string = '19 March, 2021 21:23'

# Convert date string to datetime object

date_object = datetime.strptime(date_string, "%d %B, %Y")

print(date_object)

Let’s run the code to see what happens:

~/opt/anaconda3/lib/python3.8/_strptime.py in _strptime(data_string, format)
    350                          (data_string, format))
    351     if len(data_string) != found.end():
--> 352         raise ValueError("unconverted data remains: %s" %
    353                           data_string[found.end():])
    354 

ValueError: unconverted data remains:  21:23

The error occurs because the part of the string ‘21:23‘ does not match the format_code ‘%d %B, %Y‘

Solution

To solve this error we need to include hours and minutes in the format code. The format code for hours is %H and for minutes is %M. Let’s look at the revised code:

from datetime import datetime

# Define date string

date_string = '19 March, 2021 21:23'

# Convert date string to datetime object

date_object = datetime.strptime(date_string, "%d %B, %Y %H:%M")

print(date_object)

Let’s run the code to see the result:

2021-03-19 21:23:00

We successfully converted the string to a datetime object using datetime.strptime().

Format Code List

Format code	Meaning	Example
%a	Abbreviated weekday name	Sun, Mon,…
%A	Full weekday name	Sunday, Monday, …
%w	Weekday as a decimal number	0, 1, …, 6
%d	Day of the month as a zero-padded decimal	01, 02, …, 31
%-d	Day of the month as a decimal number	1, 2, …, 30
%b	Abbreviated month name	Jan, Feb, …, Dec
%B	Full month name	January, February, …
%m	Month as a zero-padded decimal number	01, 02, …, 12
%-m	Month as a decimal number	1, 2, …, 12
%y	Year without century as a zero-padded decimal number	00, 01, …, 99
%-y	Year without century as a decimal number	0, 1, …, 99
%Y	Year with century as a decimal number	2013, 2014, …
%H	Hour (24-hour clock) as a zero-padded decimal number	00, 01, …, 23
%-H	Hour (24-hour clock) as a decimal number	0, 1, …, 23
%I	Hour (12-hour clock) as a zero-padded decimal number	01, 02, …, 12
%-I	Hour (12-hour clock) as a zero-padded decimal number	1, 2, …, 12
%p	Locale’s AM or PM	AM, PM
%M	Minute as a zero-padded decimal number	00, 01, …, 59
%-M	Minute as a decimal number	0, 1, …, 59
%S	Second as a zero-padded number	00, 01, …, 59
%-S	Second as a decimal number	0, 1, …, 59
%f	Microsecond as a decimal number, zero-padded on the left	000000 – 999999
%z	UTC offset in the form +HHMM or -HHMM
%Z	Time zone name
%j	Day of the year as a zero-padded decimal number	001, 002, …, 366
%-j	Day of the year as a decimal number	1, 2, …, 366
%U	Week number of the year (Sunday as the first day of the week). All days in a new year preceding the first Sunday are in week 0	00, 01, …, 53
%W	Week number of the year (Monday as the first day of the week). All days in a new year preceding the first Monday are in week 0	00, 01, …, 53
%c	Locale’s appropriate date and time representation	Mon Apr 11 08:56:02 2022
%x	Locale’s appropriate date representation	04/11/22
%X	Locale’s appropriate time representation	08:56:02
%%	A Literal ‘%’ character	%

Summary

Congratulations on reading to the end of this tutorial! The ValueError: unconverted data remains occurs when the string has a format that does not match the format code of the datetime.strptime() method.

For further reading on datetime objects, go to the article: How to Solve Python AttributeError: ‘Series’ object has no attribute ‘strftime’

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