Lib/calendar.py
cpython 3.14 @ ab2d84fe1023/Lib/calendar.py
calendar provides a class hierarchy for rendering months and years as formatted text or HTML. The root Calendar class handles the date arithmetic: iterating over the weeks of a month, deciding which day a week starts on, and padding weeks so every row has exactly seven entries. Concrete subclasses (TextCalendar, HTMLCalendar) add rendering logic without reimplementing the iteration.
The module also ships a family of locale-aware subclasses (LocaleTextCalendar, LocaleHTMLCalendar) that temporarily switch the process locale to produce month and weekday names in a target language. Module-level convenience functions (month, calendar, prmonth, prcal) delegate to a shared TextCalendar instance so callers do not have to construct objects for simple use cases.
A small set of standalone utility functions covers leap-year logic (isleap, leapdays), week-of-year calculation, and monthrange / monthcalendar which are the building blocks used throughout the class hierarchy. The module also exposes a command-line interface for printing calendars directly from a shell.
Map
| Lines | Symbol | Role | gopy |
|---|---|---|---|
| 1-50 | module constants, setfirstweekday | Weekday constants, locale helpers | - |
| 51-130 | isleap, leapdays, weekday, weekheader, monthrange | Date arithmetic utilities | - |
| 131-210 | Calendar base class | itermonthdates, monthdayscalendar, week iteration | - |
| 211-320 | TextCalendar | Plain-text month and year formatting | - |
| 321-430 | HTMLCalendar | HTML <table> month and year formatting | - |
| 431-510 | LocaleTextCalendar, LocaleHTMLCalendar | Locale-switched name variants | - |
| 511-580 | module-level convenience functions | month, calendar, prmonth, prcal | - |
| 581-640 | monthcalendar, timegm | Additional standalone utilities | - |
| 641-680 | __main__ block | CLI argument parsing and output | - |
Reading
Utility functions: leap year and month range (lines 51 to 130)
cpython 3.14 @ ab2d84fe1023/Lib/calendar.py#L51-130
isleap(year) applies the Gregorian rule: divisible by 4, except centuries unless also divisible by 400. leapdays(y1, y2) counts leap years in the half-open interval [y1, y2) using integer division rather than a loop. monthrange(year, month) returns a (weekday_of_first, days_in_month) pair and is the single place where the calendar grid is anchored to real dates.
def isleap(year):
return year % 4 == 0 and (year % 100 != 0 or year % 400 == 0)
def monthrange(year, month):
day1 = weekday(year, month, 1)
ndays = mdays[month] + (month == February and isleap(year))
return day1, ndays
Calendar base class and itermonthdates (lines 131 to 210)
cpython 3.14 @ ab2d84fe1023/Lib/calendar.py#L131-210
Calendar.__init__ accepts a firstweekday argument (0 = Monday, 6 = Sunday). itermonthdates(year, month) yields datetime.date objects covering the full display weeks of a month, padding before the first and after the last day so every yielded sequence length is a multiple of seven. itermonthdays and itermonthdays2 are lighter variants that yield integers (day numbers, 0 for padding) or (day, weekday) pairs without constructing date objects.
def itermonthdates(self, year, month):
for d in self.itermonthdays2(year, month):
...
yield datetime.date(year, month, d[0])
TextCalendar formatting (lines 211 to 320)
cpython 3.14 @ ab2d84fe1023/Lib/calendar.py#L211-320
TextCalendar.formatmonth(theyear, themonth, w=0, l=0) builds a multi-line string. It calls formatweek for each row returned by monthdayscalendar, prepends a two-line header produced by formatmonthname and formatweekheader, and joins everything with l newlines between rows. Column width w controls zero-padding of day numbers. formatyear tiles twelve months in three columns separated by c spaces.
def formatmonth(self, theyear, themonth, w=0, l=0):
v = []
...
v.append(self.formatmonthname(theyear, themonth, 7*(w+1)-1))
v.append(self.formatweekheader(w).rstrip())
for week in self.monthdays2calendar(theyear, themonth):
v.append(self.formatweek(week, w).rstrip())
return '\n'.join(v)
HTMLCalendar (lines 321 to 430)
cpython 3.14 @ ab2d84fe1023/Lib/calendar.py#L321-430
HTMLCalendar overrides the format methods to emit <table>, <tr>, and <td> tags. Each <td> carries a CSS class: the weekday name for ordinary days (mon, tue, ...) and noday for padding cells. formatyear wraps the twelve month tables in a single outer table with class year. The CSS class names are defined as a class-level tuple so subclasses can override them without reimplementing the rendering methods.
cssclasses = ["mon", "tue", "wed", "thu", "fri", "sat", "sun"]
def formatday(self, day, weekday):
if day == 0:
return '<td class="noday"> </td>'
else:
return '<td class="%s">%d</td>' % (self.cssclasses[weekday], day)
Locale-aware subclasses (lines 431 to 510)
cpython 3.14 @ ab2d84fe1023/Lib/calendar.py#L431-510
LocaleTextCalendar and LocaleHTMLCalendar accept a locale argument. They override formatweekday and formatmonthname to call locale.setlocale around datetime formatting calls that produce locale-dependent names. A contextmanager-based helper restores the original locale even if formatting raises an exception, preventing locale state from leaking across calls.
class LocaleTextCalendar(TextCalendar):
def __init__(self, firstweekday=0, locale=None):
super().__init__(firstweekday)
...
def formatweekday(self, day, width):
with TimeEncoding(self.locale) as encoding:
...
gopy mirror
Not yet ported.