How to Parse Dates from Week Numbers Using datetime.strptime()?

Datetime Strptime() and Week Numbers

This query addresses an issue with utilizing datetime.strptime() to parse a date from a week number. The following code snippet demonstrates the problem:

import datetime
d = "2013-W26"
r = datetime.datetime.strptime(d, "%Y-W%W")
print(r)

The expected output is "2013-01-01 00:00:00", but the code yields an error due to insufficient information.

The Solution

To resolve this issue, we need to provide a specific day of the week for the specified week number. We can do this by adding a default day, such as Monday:

import datetime
d = "2013-W26"
r = datetime.datetime.strptime(d + '-1', "%Y-W%W-%w")
print(r)

The '-1' in the format string indicates Monday. This results in the correct output of:

2013-07-01 00:00:00

Key Points

• Week numbers (%W and %U) in strptime() require both the day of the week and the year to be specified for accurate parsing.
• Monday is typically used as the first day of the week when parsing week numbers.
• For ISO week dates, use the directives %G-W%V-%u instead (requires Python 3.6 or newer).

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