PyMOTW-3calendar — Work with Dates¶
| Purpose: | The calendar module implements classes for working with dates to manage year/month/week oriented values. |
|---|
The calendar module defines the Calendar class, which
encapsulates calculations for values such as the dates of the weeks in
a given month or year. In addition, the TextCalendar and
HTMLCalendar classes can produce pre-formatted output.
Formatting Examples¶
The prmonth() method is a simple function that produces the
formatted text output for a month.
import calendar
c = calendar.TextCalendar(calendar.SUNDAY)
c.prmonth(2017, 7)
The example configures TextCalendar to start weeks on Sunday,
following the American convention. The default is to use the European
convention of starting a week on Monday.
The output looks like:
$ python3 calendar_textcalendar.py
July 2017
Su Mo Tu We Th Fr Sa
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31
A similar HTML table can be produced with HTMLCalendar and
formatmonth(). The rendered output looks roughly the same as
the plain text version, but is wrapped with HTML tags. Each table
cell has a class attribute corresponding to the day of the week, so
the HTML can be styled through CSS.
To produce output in a format other than one of the available
defaults, use calendar to calculate the dates and organize the
values into week and month ranges, then iterate over the result. The
weekheader(), monthcalendar(), and
yeardays2calendar() methods of Calendar are especially
useful for that.
Calling yeardays2calendar() produces a sequence of “month row”
lists. Each list includes the months as another list of weeks. The
weeks are lists of tuples made up of day number (1-31) and weekday
number (0-6). Days that fall outside of the month have a day number of
0.
import calendar
import pprint
cal = calendar.Calendar(calendar.SUNDAY)
cal_data = cal.yeardays2calendar(2017, 3)
print('len(cal_data) :', len(cal_data))
top_months = cal_data[0]
print('len(top_months) :', len(top_months))
first_month = top_months[0]
print('len(first_month) :', len(first_month))
print('first_month:')
pprint.pprint(first_month, width=65)
Calling yeardays2calendar(2017, 3) returns data for 2017,
organized with three months per row.
$ python3 calendar_yeardays2calendar.py
len(cal_data) : 4
len(top_months) : 3
len(first_month) : 5
first_month:
[[(1, 6), (2, 0), (3, 1), (4, 2), (5, 3), (6, 4), (7, 5)],
[(8, 6), (9, 0), (10, 1), (11, 2), (12, 3), (13, 4), (14, 5)],
[(15, 6), (16, 0), (17, 1), (18, 2), (19, 3), (20, 4), (21,
5)],
[(22, 6), (23, 0), (24, 1), (25, 2), (26, 3), (27, 4), (28,
5)],
[(29, 6), (30, 0), (31, 1), (0, 2), (0, 3), (0, 4), (0, 5)]]
This is equivalent to the data used by formatyear().
import calendar
cal = calendar.TextCalendar(calendar.SUNDAY)
print(cal.formatyear(2017, 2, 1, 1, 3))
For the same arguments, formatyear() produces this output:
$ python3 calendar_formatyear.py
2017
January February March
Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa
1 2 3 4 5 6 7 1 2 3 4 1 2 3 4
8 9 10 11 12 13 14 5 6 7 8 9 10 11 5 6 7 8 9 10 11
15 16 17 18 19 20 21 12 13 14 15 16 17 18 12 13 14 15 16 17 18
22 23 24 25 26 27 28 19 20 21 22 23 24 25 19 20 21 22 23 24 25
29 30 31 26 27 28 26 27 28 29 30 31
April May June
Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa
1 1 2 3 4 5 6 1 2 3
2 3 4 5 6 7 8 7 8 9 10 11 12 13 4 5 6 7 8 9 10
9 10 11 12 13 14 15 14 15 16 17 18 19 20 11 12 13 14 15 16 17
16 17 18 19 20 21 22 21 22 23 24 25 26 27 18 19 20 21 22 23 24
23 24 25 26 27 28 29 28 29 30 31 25 26 27 28 29 30
30
July August September
Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa
1 1 2 3 4 5 1 2
2 3 4 5 6 7 8 6 7 8 9 10 11 12 3 4 5 6 7 8 9
9 10 11 12 13 14 15 13 14 15 16 17 18 19 10 11 12 13 14 15 16
16 17 18 19 20 21 22 20 21 22 23 24 25 26 17 18 19 20 21 22 23
23 24 25 26 27 28 29 27 28 29 30 31 24 25 26 27 28 29 30
30 31
October November December
Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa
1 2 3 4 5 6 7 1 2 3 4 1 2
8 9 10 11 12 13 14 5 6 7 8 9 10 11 3 4 5 6 7 8 9
15 16 17 18 19 20 21 12 13 14 15 16 17 18 10 11 12 13 14 15 16
22 23 24 25 26 27 28 19 20 21 22 23 24 25 17 18 19 20 21 22 23
29 30 31 26 27 28 29 30 24 25 26 27 28 29 30
31
The day_name, day_abbr, month_name, and
month_abbr module attributes useful for producing custom
formatted output (i.e., to include links in the HTML output). They are
automatically configured correctly for the current locale.
Locales¶
To produce a calendar formatted for a locale other than the current
default, use LocaleTextCalendar or
LocaleHTMLCalendar.
import calendar
c = calendar.LocaleTextCalendar(locale='en_US')
c.prmonth(2017, 7)
print()
c = calendar.LocaleTextCalendar(locale='fr_FR')
c.prmonth(2017, 7)
The first day of the week is not part of the locale settings, and the
value is taken from the argument to the calendar class just as with
the regular TextCalendar.
$ python3 calendar_locale.py
July 2017
Mo Tu We Th Fr Sa Su
1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31
juillet 2017
Lu Ma Me Je Ve Sa Di
1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31
Calculating Dates¶
Although the calendar module focuses mostly on printing full calendars
in various formats, it also provides functions useful for working with
dates in other ways, such as calculating dates for a recurring
event. For example, the Python Atlanta User’s Group meets on the
second Thursday of every month. To calculate the dates for the
meetings for a year, use the return value of monthcalendar().
import calendar
import pprint
pprint.pprint(calendar.monthcalendar(2017, 7))
Some days have a 0 value. Those are days of the week that overlap with the given month, but that are part of another month.
$ python3 calendar_monthcalendar.py
[[0, 0, 0, 0, 0, 1, 2],
[3, 4, 5, 6, 7, 8, 9],
[10, 11, 12, 13, 14, 15, 16],
[17, 18, 19, 20, 21, 22, 23],
[24, 25, 26, 27, 28, 29, 30],
[31, 0, 0, 0, 0, 0, 0]]
The first day of the week defaults to Monday. It is possible to change
that by calling setfirstweekday(), but since the calendar module
includes constants for indexing into the date ranges returned by
monthcalendar(), it is more convenient to skip that step in this
case.
To calculate the group meeting dates for a year, assuming they are
always on the second Thursday of every month, look at the output of
monthcalendar() to find the dates on which Thursdays fall. The
first and last week of the month are padded with 0 values as
placeholders for the days falling in the preceding or subsequent
month. For example, if a month starts on a Friday, the value in the
first week in the Thursday position will be 0.
import calendar
import sys
year = int(sys.argv[1])
# Show every month
for month in range(1, 13):
# Compute the dates for each week that overlaps the month
c = calendar.monthcalendar(year, month)
first_week = c[0]
second_week = c[1]
third_week = c[2]
# If there is a Thursday in the first week,
# the second Thursday is # in the second week.
# Otherwise, the second Thursday must be in
# the third week.
if first_week[calendar.THURSDAY]:
meeting_date = second_week[calendar.THURSDAY]
else:
meeting_date = third_week[calendar.THURSDAY]
print('{:>3}: {:>2}'.format(calendar.month_abbr[month],
meeting_date))
So the meeting schedule for the year is:
$ python3 calendar_secondthursday.py 2017
Jan: 12
Feb: 9
Mar: 9
Apr: 13
May: 11
Jun: 8
Jul: 13
Aug: 10
Sep: 14
Oct: 12
Nov: 9
Dec: 14
See also
- Standard library documentation for calendar
time– Lower-level time functions.datetime– Manipulate date values, including timestamps and time zones.locale– Locale settings.
