"calendar" — General calendar-related functions
***********************************************

**Source code:** Lib/calendar.py

======================================================================

This module allows you to output calendars like the Unix **cal**
program, and provides additional useful functions related to the
calendar. By default, these calendars have Monday as the first day of
the week, and Sunday as the last (the European convention). Use
"setfirstweekday()" to set the first day of the week to Sunday (6) or
to any other weekday.  Parameters that specify dates are given as
integers. For related functionality, see also the "datetime" and
"time" modules.

The functions and classes defined in this module use an idealized
calendar, the current Gregorian calendar extended indefinitely in both
directions.  This matches the definition of the “proleptic Gregorian”
calendar in Dershowitz and Reingold’s book “Calendrical Calculations”,
where it’s the base calendar for all computations.  Zero and negative
years are interpreted as prescribed by the ISO 8601 standard.  Year 0
is 1 BC, year -1 is 2 BC, and so on.

class calendar.Calendar(firstweekday=0)

   Creates a "Calendar" object. *firstweekday* is an integer
   specifying the first day of the week. "0" is Monday (the default),
   "6" is Sunday.

   A "Calendar" object provides several methods that can be used for
   preparing the calendar data for formatting. This class doesn’t do
   any formatting itself. This is the job of subclasses.

   "Calendar" instances have the following methods:

   iterweekdays()

      Return an iterator for the week day numbers that will be used
      for one week.  The first value from the iterator will be the
      same as the value of the "firstweekday" property.

   itermonthdates(year, month)

      Return an iterator for the month *month* (1–12) in the year
      *year*. This iterator will return all days (as "datetime.date"
      objects) for the month and all days before the start of the
      month or after the end of the month that are required to get a
      complete week.

   itermonthdays(year, month)

      Return an iterator for the month *month* in the year *year*
      similar to "itermonthdates()", but not restricted by the
      "datetime.date" range. Days returned will simply be day of the
      month numbers.  For the days outside of the specified month, the
      day number is "0".

   itermonthdays2(year, month)

      Return an iterator for the month *month* in the year *year*
      similar to "itermonthdates()", but not restricted by the
      "datetime.date" range. Days returned will be tuples consisting
      of a day of the month number and a week day number.

   itermonthdays3(year, month)

      Return an iterator for the month *month* in the year *year*
      similar to "itermonthdates()", but not restricted by the
      "datetime.date" range. Days returned will be tuples consisting
      of a year, a month and a day of the month numbers.

      New in version 3.7.

   itermonthdays4(year, month)

      Return an iterator for the month *month* in the year *year*
      similar to "itermonthdates()", but not restricted by the
      "datetime.date" range. Days returned will be tuples consisting
      of a year, a month, a day of the month, and a day of the week
      numbers.

      New in version 3.7.

   monthdatescalendar(year, month)

      Return a list of the weeks in the month *month* of the *year* as
      full weeks.  Weeks are lists of seven "datetime.date" objects.

   monthdays2calendar(year, month)

      Return a list of the weeks in the month *month* of the *year* as
      full weeks.  Weeks are lists of seven tuples of day numbers and
      weekday numbers.

   monthdayscalendar(year, month)

      Return a list of the weeks in the month *month* of the *year* as
      full weeks.  Weeks are lists of seven day numbers.

   yeardatescalendar(year, width=3)

      Return the data for the specified year ready for formatting. The
      return value is a list of month rows. Each month row contains up
      to *width* months (defaulting to 3). Each month contains between
      4 and 6 weeks and each week contains 1–7 days. Days are
      "datetime.date" objects.

   yeardays2calendar(year, width=3)

      Return the data for the specified year ready for formatting
      (similar to "yeardatescalendar()"). Entries in the week lists
      are tuples of day numbers and weekday numbers. Day numbers
      outside this month are zero.

   yeardayscalendar(year, width=3)

      Return the data for the specified year ready for formatting
      (similar to "yeardatescalendar()"). Entries in the week lists
      are day numbers. Day numbers outside this month are zero.

class calendar.TextCalendar(firstweekday=0)

   This class can be used to generate plain text calendars.

   "TextCalendar" instances have the following methods:

   formatmonth(theyear, themonth, w=0, l=0)

      Return a month’s calendar in a multi-line string. If *w* is
      provided, it specifies the width of the date columns, which are
      centered. If *l* is given, it specifies the number of lines that
      each week will use. Depends on the first weekday as specified in
      the constructor or set by the "setfirstweekday()" method.

   prmonth(theyear, themonth, w=0, l=0)

      Print a month’s calendar as returned by "formatmonth()".

   formatyear(theyear, w=2, l=1, c=6, m=3)

      Return a *m*-column calendar for an entire year as a multi-line
      string. Optional parameters *w*, *l*, and *c* are for date
      column width, lines per week, and number of spaces between month
      columns, respectively. Depends on the first weekday as specified
      in the constructor or set by the "setfirstweekday()" method.
      The earliest year for which a calendar can be generated is
      platform-dependent.

   pryear(theyear, w=2, l=1, c=6, m=3)

      Print the calendar for an entire year as returned by
      "formatyear()".

class calendar.HTMLCalendar(firstweekday=0)

   This class can be used to generate HTML calendars.

   "HTMLCalendar" instances have the following methods:

   formatmonth(theyear, themonth, withyear=True)

      Return a month’s calendar as an HTML table. If *withyear* is
      true the year will be included in the header, otherwise just the
      month name will be used.

   formatyear(theyear, width=3)

      Return a year’s calendar as an HTML table. *width* (defaulting
      to 3) specifies the number of months per row.

   formatyearpage(theyear, width=3, css='calendar.css', encoding=None)

      Return a year’s calendar as a complete HTML page. *width*
      (defaulting to 3) specifies the number of months per row. *css*
      is the name for the cascading style sheet to be used. "None" can
      be passed if no style sheet should be used. *encoding* specifies
      the encoding to be used for the output (defaulting to the system
      default encoding).

   "HTMLCalendar" has the following attributes you can override to
   customize the CSS classes used by the calendar:

   cssclasses

      A list of CSS classes used for each weekday. The default class
      list is:

         cssclasses = ["mon", "tue", "wed", "thu", "fri", "sat", "sun"]

      more styles can be added for each day:

         cssclasses = ["mon text-bold", "tue", "wed", "thu", "fri", "sat", "sun red"]

      Note that the length of this list must be seven items.

   cssclass_noday

      The CSS class for a weekday occurring in the previous or coming
      month.

      New in version 3.7.

   cssclasses_weekday_head

      A list of CSS classes used for weekday names in the header row.
      The default is the same as "cssclasses".

      New in version 3.7.

   cssclass_month_head

      The month’s head CSS class (used by "formatmonthname()"). The
      default value is ""month"".

      New in version 3.7.

   cssclass_month

      The CSS class for the whole month’s table (used by
      "formatmonth()"). The default value is ""month"".

      New in version 3.7.

   cssclass_year

      The CSS class for the whole year’s table of tables (used by
      "formatyear()"). The default value is ""year"".

      New in version 3.7.

   cssclass_year_head

      The CSS class for the table head for the whole year (used by
      "formatyear()"). The default value is ""year"".

      New in version 3.7.

   Note that although the naming for the above described class
   attributes is singular (e.g. "cssclass_month" "cssclass_noday"),
   one can replace the single CSS class with a space separated list of
   CSS classes, for example:

      "text-bold text-red"

   Here is an example how "HTMLCalendar" can be customized:

      class CustomHTMLCal(calendar.HTMLCalendar):
          cssclasses = [style + " text-nowrap" for style in
                        calendar.HTMLCalendar.cssclasses]
          cssclass_month_head = "text-center month-head"
          cssclass_month = "text-center month"
          cssclass_year = "text-italic lead"

class calendar.LocaleTextCalendar(firstweekday=0, locale=None)

   This subclass of "TextCalendar" can be passed a locale name in the
   constructor and will return month and weekday names in the
   specified locale. If this locale includes an encoding all strings
   containing month and weekday names will be returned as unicode.

class calendar.LocaleHTMLCalendar(firstweekday=0, locale=None)

   This subclass of "HTMLCalendar" can be passed a locale name in the
   constructor and will return month and weekday names in the
   specified locale. If this locale includes an encoding all strings
   containing month and weekday names will be returned as unicode.

Note:

  The "formatweekday()" and "formatmonthname()" methods of these two
  classes temporarily change the current locale to the given *locale*.
  Because the current locale is a process-wide setting, they are not
  thread-safe.

For simple text calendars this module provides the following
functions.

calendar.setfirstweekday(weekday)

   Sets the weekday ("0" is Monday, "6" is Sunday) to start each week.
   The values "MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY",
   "SATURDAY", and "SUNDAY" are provided for convenience. For example,
   to set the first weekday to Sunday:

      import calendar
      calendar.setfirstweekday(calendar.SUNDAY)

calendar.firstweekday()

   Returns the current setting for the weekday to start each week.

calendar.isleap(year)

   Returns "True" if *year* is a leap year, otherwise "False".

calendar.leapdays(y1, y2)

   Returns the number of leap years in the range from *y1* to *y2*
   (exclusive), where *y1* and *y2* are years.

   This function works for ranges spanning a century change.

calendar.weekday(year, month, day)

   Returns the day of the week ("0" is Monday) for *year* ("1970"–…),
   *month* ("1"–"12"), *day* ("1"–"31").

calendar.weekheader(n)

   Return a header containing abbreviated weekday names. *n* specifies
   the width in characters for one weekday.

calendar.monthrange(year, month)

   Returns weekday of first day of the month and number of days in
   month,  for the specified *year* and *month*.

calendar.monthcalendar(year, month)

   Returns a matrix representing a month’s calendar.  Each row
   represents a week; days outside of the month are represented by
   zeros. Each week begins with Monday unless set by
   "setfirstweekday()".

calendar.prmonth(theyear, themonth, w=0, l=0)

   Prints a month’s calendar as returned by "month()".

calendar.month(theyear, themonth, w=0, l=0)

   Returns a month’s calendar in a multi-line string using the
   "formatmonth()" of the "TextCalendar" class.

calendar.prcal(year, w=0, l=0, c=6, m=3)

   Prints the calendar for an entire year as returned by
   "calendar()".

calendar.calendar(year, w=2, l=1, c=6, m=3)

   Returns a 3-column calendar for an entire year as a multi-line
   string using the "formatyear()" of the "TextCalendar" class.

calendar.timegm(tuple)

   An unrelated but handy function that takes a time tuple such as
   returned by the "gmtime()" function in the "time" module, and
   returns the corresponding Unix timestamp value, assuming an epoch
   of 1970, and the POSIX encoding.  In fact, "time.gmtime()" and
   "timegm()" are each others’ inverse.

The "calendar" module exports the following data attributes:

calendar.day_name

   An array that represents the days of the week in the current
   locale.

calendar.day_abbr

   An array that represents the abbreviated days of the week in the
   current locale.

calendar.month_name

   An array that represents the months of the year in the current
   locale.  This follows normal convention of January being month
   number 1, so it has a length of 13 and  "month_name[0]" is the
   empty string.

calendar.month_abbr

   An array that represents the abbreviated months of the year in the
   current locale.  This follows normal convention of January being
   month number 1, so it has a length of 13 and  "month_abbr[0]" is
   the empty string.

See also:

  Module "datetime"
     Object-oriented interface to dates and times with similar
     functionality to the "time" module.

  Module "time"
     Low-level time related functions.
