date.isocalendar() to get ISO year, ISO week number, ISO weekday from date object

isocalendar() : to get ISO year, ISO week number, ISO weekday

Today's isocalendar()

from datetime import date

dt = date.today()
print(dt.isocalendar())

Output ( will change based on current date )

(2019, 38, 2)

The date.isocalendar() function returns a tuple with the ISO year, ISO week number, and ISO weekday for a given date. This is especially useful for analyzing data by week or aligning with ISO standards in project timelines.

Using date and time object

from datetime import date

dt = date(2019, 12, 31)
print(dt.isocalendar())

Output

datetime.IsoCalendarDate(year=2020, week=1, weekday=2)

Syntax

date_object.isocalendar()

Example 2: ISO Calendar for a Specific Date

Calculate the ISO week and weekday for a specified date.

from datetime import date

specific_date = date(2022, 12, 31)
print(specific_date.isocalendar())

Output:

datetime.IsoCalendarDate(year=2022, week=52, weekday=6)

Example 3: Using ISO Week in a Loop

Iterate over a range of dates and print the ISO week for each.

from datetime import date, timedelta

start_date = date(2024, 12, 25)
for i in range(7):
    current_date = start_date + timedelta(days=i)
    iso_year, iso_week, iso_weekday = current_date.isocalendar()
    print(f"Date: {current_date}, ISO Week: {iso_week}")

Output

Date: 2024-12-25, ISO Week: 52
Date: 2024-12-26, ISO Week: 52
Date: 2024-12-27, ISO Week: 52
Date: 2024-12-28, ISO Week: 52
Date: 2024-12-29, ISO Week: 52
Date: 2024-12-30, ISO Week: 1 
Date: 2024-12-31, ISO Week: 1

Example 4: Creating a Week-Based Report

This example demonstrates creating a weekly summary using ISO weeks.

from datetime import date, timedelta

dates = [date(2022, 12, 24), 
          date(2022, 12, 25), 
          date(2023, 1, 1)]

week_summary = {}

for d in dates:
    iso_week = d.isocalendar()[1]
    week_summary[iso_week] = week_summary.get(iso_week, 0) + 1

print("Weekly summary:", week_summary)

Output:

Weekly summary: {51: 2, 52: 1}

Applications of isocalendar()

Weekly Reports: Track data by ISO week for consistent reporting.
Project Management: Align project milestones with ISO-standard weeks.
Fiscal Year Calculations: Use ISO year and week for fiscal or academic reporting.

All Date Objects

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isocalendar(): Extract ISO Year, Week Number, and Weekday