Bug #947906: An object oriented interface has been added to the calendar

module. It's possible to generate HTML calendar now and the module can be
called as a script (e.g. via ``python -mcalendar``).

4 files changed, 703 insertions, 169 deletions

diff --git a/Doc/lib/libcalendar.tex b/Doc/lib/libcalendar.tex
index bf3a7d6..eb40008 100644
--- a/Doc/lib/libcalendar.tex
+++ b/Doc/lib/libcalendar.tex
@@ -15,12 +15,137 @@ convention). Use \function{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.
 
-Most of these functions rely on the \module{datetime} module which
-uses an idealized calendar, the current Gregorian calendar indefinitely
-extended 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.
+Most of these functions and classses rely on the \module{datetime}
+module which uses an idealized calendar, the current Gregorian
+calendar indefinitely extended 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.
+
+\begin{classdesc}{Calendar}{\optional{firstweekday}}
+Creates a \class{Calendar} object. \var{firstweekday} is an integer
+specifying the first day of the week. 0 is Monday, 6 is Sunday.
+
+A \class{Calendar} object provides several method 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.
+\versionadded{2.5}
+
+\begin{methoddesc}{firstweekday}{}
+Return the first day of the week (as specified in the constructor
+or changed via \method{setfirstweekday()}.
+
+\begin{methoddesc}{setfirstweekday}{weekday}
+Set the first day of the week.
+
+\begin{methoddesc}{iterweekdays}{weekday}
+Return an iterator for the week day numbers that will be used
+for one week. The first number from the iterator will be the
+same as the number return by \method{firstweekday()}.
+
+\begin{methoddesc}{itermonthdates}{year, month}
+Return an iterator for the month \var{month} (1-12) in the
+year \var{year}. This iterator will return all days (as
+\class{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.
+
+\begin{methoddesc}{itermonthdays2}{year, month}
+Return an iterator for the month \var{month} in the year
+\var{year} similar to \method{itermonthdates()}. Days returned
+will be tuple consisting of a day number and a week day
+number.
+
+\begin{methoddesc}{itermonthdays}{year, month}
+Return an iterator for the month \var{month} in the year
+\var{year} similar to \method{itermonthdates()}. Days returned
+will simply be day numbers.
+
+\begin{methoddesc}{monthdatescalendar}{year, month}
+Return a list of the weeks in the month \var{month} of
+the \var{year} as full weeks. Weeks are lists of seven
+\class{datetime.date} objects.
+
+\begin{methoddesc}{monthdays2calendar}{year, month}
+Return a list of the weeks in the month \var{month} of
+the \var{year} as full weeks. Weeks are lists of seven
+tuples of day numbers and weekday numbers.
+
+\begin{methoddesc}{monthdayscalendar}{year, month}
+Return a list of the weeks in the month \var{month} of
+the \var{year} as full weeks. Weeks are lists of seven
+day numbers.
+
+\begin{methoddesc}{yeardatescalendar}{year, month\optional{, width}}
+Return the data for the specified year ready for formatting. The return
+value is a list of month rows. Each month row contains upto \var{width}
+months (defaulting to 3). Each month contains between 4 and 6 weeks and
+each week contains 1-7 days. Days are \class{datetime.date} objects.
+
+\begin{methoddesc}{yeardays2calendar}{year, month\optional{, width}}
+Return the data for the specified year ready for formatting (similar to
+\method{yeardatescalendar()}). Entries in the week lists are tuples of
+day numbers and weekday numbers. Day numbers outside this month are zero.
+
+\begin{methoddesc}{yeardayscalendar}{year, month\optional{, width}}
+Return the data for the specified year ready for formatting (similar to
+\method{yeardatescalendar()}). Entries in the week lists are day numbers.
+Day numbers outside this month are zero.
+
+
+\begin{classdesc}{TextCalendar}{\optional{firstweekday}}
+This class can be used for generating plain text calendars.
+
+\versionadded{2.5}
+
+\begin{methoddesc}{formatmonth}{theyear, themonth\optional{, w\optional{, l}}}
+Returns a month's calendar in a multi-line string. If \var{w} is
+provided, it specifies the width of the date columns, which are
+centered. If \var{l} is given, it specifies the number of lines that
+each week will use. Depends on the first weekday as set by
+\function{setfirstweekday()}.
+
+\begin{methoddesc}{prmonth}{theyear, themonth\optional{, w\optional{, l}}}
+Prints a month's calendar as returned by \method{formatmonth()}.
+
+\begin{methoddesc}{formatyear}{theyear, themonth\optional{, w\optional{, l\optional{, c\optional{, m}}}}}
+Returns a \var{m}-column calendar for an entire year as a multi-line string.
+Optional parameters \var{w}, \var{l}, and \var{c} are for date column
+width, lines per week, and number of spaces between month columns,
+respectively. Depends on the first weekday as set by
+\method{setfirstweekday()}.  The earliest year for which a calendar can
+be generated is platform-dependent.
+
+\begin{methoddesc}{pryear}{theyear\optional{, w\optional{, l\optional{, c\optional{, m}}}}}
+Prints the calendar for an entire year as returned by  \method{formatyear()}.
+\end{funcdesc}
+
+
+\begin{classdesc}{HTMLCalendar}{\optional{firstweekday}}
+This class can be used for generating HTML calendars.
+
+\versionadded{2.5}
+
+\begin{methoddesc}{formatmonth}{theyear, themonth\optional{, withyear}}
+Returns a month's calendar as an HTML table. If \var{withyear} is
+true the year will be included in the header, otherwise just the
+monthname will be used.
+
+\begin{methoddesc}{formatyear}{theyear, themonth\optional{, width}}
+Returns a year's calendar as an HTML table. \var{width} (defaulting to 3)
+specifies the number of months per row.
+
+\begin{methoddesc}{formatyearpage}{theyear, themonth\optional{, width\optional{, css\optional{, encoding}}}}
+Returns a year's calendar as an complete HTML page. \var{width}
+(defaulting to 3) specifies the number of months per row. \var{css}
+is the name for the cascading style sheet to be used. \constant{None}
+can be passed, if no style sheet should be used. \var{encoding}
+specifies the encoding to be used for the output (defaulting
+the the system default encoding).
+
+
+For simple text calendars this module provides the following functions.
 
 \begin{funcdesc}{setfirstweekday}{weekday}
 Sets the weekday (\code{0} is Monday, \code{6} is Sunday) to start
@@ -80,11 +205,8 @@ Prints a month's calendar as returned by \function{month()}.
 \end{funcdesc}
 
 \begin{funcdesc}{month}{theyear, themonth\optional{, w\optional{, l}}}
-Returns a month's calendar in a multi-line string. If \var{w} is
-provided, it specifies the width of the date columns, which are
-centered. If \var{l} is given, it specifies the number of lines that
-each week will use. Depends on the first weekday as set by
-\function{setfirstweekday()}.
+Returns a month's calendar in a multi-line string using the
+\method{formatmonth} of the \class{TextCalendar} class.
 \versionadded{2.0}
 \end{funcdesc}
 
@@ -94,12 +216,8 @@ Prints the calendar for an entire year as returned by
 \end{funcdesc}
 
 \begin{funcdesc}{calendar}{year\optional{, w\optional{, l\optional{c}}}}
-Returns a 3-column calendar for an entire year as a multi-line string.
-Optional parameters \var{w}, \var{l}, and \var{c} are for date column
-width, lines per week, and number of spaces between month columns,
-respectively. Depends on the first weekday as set by
-\function{setfirstweekday()}.  The earliest year for which a calendar can
-be generated is platform-dependent.
+Returns a 3-column calendar for an entire year as a multi-line string
+using the \method{formatyear} of the \class{TextCalendar} class.
 \versionadded{2.0}
 \end{funcdesc}
 
diff --git a/Lib/calendar.py b/Lib/calendar.py
index 3ffcff5..7569621 100644
--- a/Lib/calendar.py
+++ b/Lib/calendar.py
@@ -5,17 +5,31 @@ 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 (0=Monday, 6=Sunday)."""
 
-import datetime
+import sys, datetime
 
-__all__ = ["error","setfirstweekday","firstweekday","isleap",
-           "leapdays","weekday","monthrange","monthcalendar",
-           "prmonth","month","prcal","calendar","timegm",
-           "month_name", "month_abbr", "day_name", "day_abbr",
-           "weekheader"]
+__all__ = ["IllegalMonthError", "IllegalWeekdayError", "setfirstweekday",
+           "firstweekday", "isleap", "leapdays", "weekday", "monthrange",
+           "monthcalendar", "prmonth", "month", "prcal", "calendar",
+           "timegm", "month_name", "month_abbr", "day_name", "day_abbr"]
 
 # Exception raised for bad input (with string parameter for details)
 error = ValueError
 
+# Exceptions raised for bad input
+class IllegalMonthError(ValueError):
+    def __init__(self, month):
+        self.month = month
+    def __str__(self):
+        return "bad month number %r; must be 1-12" % self.month
+
+
+class IllegalWeekdayError(ValueError):
+    def __init__(self, weekday):
+        self.weekday = weekday
+    def __str__(self):
+        return "bad weekday number %r; must be 0 (Monday) to 6 (Sunday)" % self.weekday
+
+
 # Constants for months referenced later
 January = 1
 February = 2
@@ -30,7 +44,7 @@ mdays = [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
 
 class _localized_month:
 
-    _months = [datetime.date(2001, i+1, 1).strftime for i in range(12)]
+    _months = [datetime.date(2001, i+1, 1).strftime for i in xrange(12)]
     _months.insert(0, lambda x: "")
 
     def __init__(self, format):
@@ -46,10 +60,11 @@ class _localized_month:
     def __len__(self):
         return 13
 
+
 class _localized_day:
 
     # January 1, 2001, was a Monday.
-    _days = [datetime.date(2001, 1, i+1).strftime for i in range(7)]
+    _days = [datetime.date(2001, 1, i+1).strftime for i in xrange(7)]
 
     def __init__(self, format):
         self.format = format
@@ -64,6 +79,7 @@ class _localized_day:
     def __len__(self):
         return 7
 
+
 # Full and abbreviated names of weekdays
 day_name = _localized_day('%A')
 day_abbr = _localized_day('%a')
@@ -75,23 +91,12 @@ month_abbr = _localized_month('%b')
 # Constants for weekdays
 (MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY) = range(7)
 
-_firstweekday = 0                       # 0 = Monday, 6 = Sunday
-
-def firstweekday():
-    return _firstweekday
-
-def setfirstweekday(weekday):
-    """Set weekday (Monday=0, Sunday=6) to start each week."""
-    global _firstweekday
-    if not MONDAY <= weekday <= SUNDAY:
-        raise ValueError, \
-              'bad weekday number; must be 0 (Monday) to 6 (Sunday)'
-    _firstweekday = weekday
 
 def isleap(year):
     """Return 1 for leap years, 0 for non-leap years."""
     return year % 4 == 0 and (year % 100 != 0 or year % 400 == 0)
 
+
 def leapdays(y1, y2):
     """Return number of leap years in range [y1, y2).
        Assume y1 <= y2."""
@@ -99,128 +104,414 @@ def leapdays(y1, y2):
     y2 -= 1
     return (y2//4 - y1//4) - (y2//100 - y1//100) + (y2//400 - y1//400)
 
+
 def weekday(year, month, day):
     """Return weekday (0-6 ~ Mon-Sun) for year (1970-...), month (1-12),
        day (1-31)."""
     return datetime.date(year, month, day).weekday()
 
+
 def monthrange(year, month):
     """Return weekday (0-6 ~ Mon-Sun) and number of days (28-31) for
        year, month."""
     if not 1 <= month <= 12:
-        raise ValueError, 'bad month number'
+        raise IllegalMonthError(month)
     day1 = weekday(year, month, 1)
     ndays = mdays[month] + (month == February and isleap(year))
     return day1, ndays
 
-def monthcalendar(year, month):
-    """Return a matrix representing a month's calendar.
-       Each row represents a week; days outside this month are zero."""
-    day1, ndays = monthrange(year, month)
-    rows = []
-    r7 = range(7)
-    day = (_firstweekday - day1 + 6) % 7 - 5   # for leading 0's in first week
-    while day <= ndays:
-        row = [0, 0, 0, 0, 0, 0, 0]
-        for i in r7:
-            if 1 <= day <= ndays: row[i] = day
-            day = day + 1
-        rows.append(row)
-    return rows
-
-def prweek(theweek, width):
-    """Print a single week (no newline)."""
-    print week(theweek, width),
-
-def week(theweek, width):
-    """Returns a single week in a string (no newline)."""
-    days = []
-    for day in theweek:
+
+class Calendar(object):
+    """
+    Base calendar class. This class doesn't do any formatting. It simply
+    provides data to subclasses.
+    """
+
+    def __init__(self, firstweekday=0):
+        self._firstweekday = firstweekday # 0 = Monday, 6 = Sunday
+
+    def firstweekday(self):
+        return self._firstweekday
+
+    def setfirstweekday(self, weekday):
+        """
+        Set weekday (Monday=0, Sunday=6) to start each week.
+        """
+        if not MONDAY <= weekday <= SUNDAY:
+            raise IllegalWeekdayError(weekday)
+        self._firstweekday = weekday
+
+    def iterweekdays(self):
+        """
+        Return a iterator for one week of weekday numbers starting with the
+        configured first one.
+        """
+        for i in xrange(self._firstweekday, self._firstweekday + 7):
+            yield i%7
+
+    def itermonthdates(self, year, month):
+        """
+        Return an iterator for one month. The iterator will yield datetime.date
+        values and will always iterate through complete weeks, so it will yield
+        dates outside the specified month.
+        """
+        date = datetime.date(year, month, 1)
+        # Go back to the beginning of the week
+        days = (date.weekday() - self._firstweekday) % 7
+        date -= datetime.timedelta(days=days)
+        oneday = datetime.timedelta(days=1)
+        while True:
+            yield date
+            date += oneday
+            if date.month != month and date.weekday() == self._firstweekday:
+                break
+
+    def itermonthdays2(self, year, month):
+        """
+        Like itermonthdates(), but will yield (day number, weekday number)
+        tuples. For days outside the specified month the day number is 0.
+        """
+        for date in self.itermonthdates(year, month):
+            if date.month != month:
+                yield (0, date.weekday())
+            else:
+                yield (date.day, date.weekday())
+
+    def itermonthdays(self, year, month):
+        """
+        Like itermonthdates(), but will yield day numbers tuples. For days
+        outside the specified month the day number is 0.
+        """
+        for date in self.itermonthdates(year, month):
+            if date.month != month:
+                yield 0
+            else:
+                yield date.day
+
+    def monthdatescalendar(self, year, month):
+        """
+        Return a matrix (list of lists) representing a month's calendar.
+        Each row represents a week; week entries are datetime.date values.
+        """
+        dates = list(self.itermonthdates(year, month))
+        return [ dates[i:i+7] for i in xrange(0, len(dates), 7) ]
+
+    def monthdays2calendar(self, year, month):
+        """
+        Return a matrix representing a month's calendar.
+        Each row represents a week; week entries are
+        (day number, weekday number) tuples. Day numbers outside this month
+        are zero.
+        """
+        days = list(self.itermonthdays2(year, month))
+        return [ days[i:i+7] for i in xrange(0, len(days), 7) ]
+
+    def monthdayscalendar(self, year, month):
+        """
+        Return a matrix representing a month's calendar.
+        Each row represents a week; days outside this month are zero.
+        """
+        days = list(self.itermonthdays(year, month))
+        return [ days[i:i+7] for i in xrange(0, len(days), 7) ]
+
+    def yeardatescalendar(self, 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 upto width months.
+        Each month contains between 4 and 6 weeks and each week contains 1-7
+        days. Days are datetime.date objects.
+        """
+        months = [
+            self.monthdatescalendar(year, i)
+            for i in xrange(January, January+12)
+        ]
+        return [months[i:i+width] for i in xrange(0, len(months), width) ]
+
+    def yeardays2calendar(self, year, width=3):
+        """
+        Return the data for the specified year ready for formatting (similar to
+        yeardatescalendar()). Entries in the week lists are
+        (day number, weekday number) tuples. Day numbers outside this month are
+        zero.
+        """
+        months = [
+            self.monthdays2calendar(year, i)
+            for i in xrange(January, January+12)
+        ]
+        return [months[i:i+width] for i in xrange(0, len(months), width) ]
+
+    def yeardayscalendar(self, 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.
+        """
+        months = [
+            self.monthdayscalendar(year, i)
+            for i in xrange(January, January+12)
+        ]
+        return [months[i:i+width] for i in xrange(0, len(months), width) ]
+
+
+class TextCalendar(Calendar):
+    """
+    Subclass of Calendar that outputs a calendar as a simple plain text
+    similar to the UNIX program cal.
+    """
+
+    def prweek(theweek, width):
+        """
+        Print a single week (no newline).
+        """
+        print self.week(theweek, width),
+
+    def formatday(self, day, weekday, width):
+        """
+        Returns a formatted day.
+        """
         if day == 0:
             s = ''
         else:
             s = '%2i' % day             # right-align single-digit days
-        days.append(s.center(width))
-    return ' '.join(days)
-
-def weekheader(width):
-    """Return a header for a week."""
-    if width >= 9:
-        names = day_name
-    else:
-        names = day_abbr
-    days = []
-    for i in range(_firstweekday, _firstweekday + 7):
-        days.append(names[i%7][:width].center(width))
-    return ' '.join(days)
-
-def prmonth(theyear, themonth, w=0, l=0):
-    """Print a month's calendar."""
-    print month(theyear, themonth, w, l),
-
-def month(theyear, themonth, w=0, l=0):
-    """Return a month's calendar string (multi-line)."""
-    w = max(2, w)
-    l = max(1, l)
-    s = ("%s %r" % (month_name[themonth], theyear)).center(
-                 7 * (w + 1) - 1).rstrip() + \
-         '\n' * l + weekheader(w).rstrip() + '\n' * l
-    for aweek in monthcalendar(theyear, themonth):
-        s = s + week(aweek, w).rstrip() + '\n' * l
-    return s[:-l] + '\n'
-
-# Spacing of month columns for 3-column year calendar
+        return s.center(width)
+
+    def formatweek(self, theweek, width):
+        """
+        Returns a single week in a string (no newline).
+        """
+        return ' '.join(self.formatday(d, wd, width) for (d, wd) in theweek)
+
+    def formatweekday(self, day, width):
+        """
+        Returns a formatted week day name.
+        """
+        if width >= 9:
+            names = day_name
+        else:
+            names = day_abbr
+        return names[day][:width].center(width)
+
+    def formatweekheader(self, width):
+        """
+        Return a header for a week.
+        """
+        return ' '.join(self.formatweekday(i, width) for i in self.iterweekdays())
+
+    def formatmonthname(self, theyear, themonth, width):
+        """
+        Return a formatted month name.
+        """
+        s = "%s %r" % (month_name[themonth], theyear)
+        return s.center(width)
+
+    def prmonth(self, theyear, themonth, w=0, l=0):
+        """
+        Print a month's calendar.
+        """
+        print self.formatmonth(theyear, themonth, w, l),
+
+    def formatmonth(self, theyear, themonth, w=0, l=0):
+        """
+        Return a month's calendar string (multi-line).
+        """
+        w = max(2, w)
+        l = max(1, l)
+        s = self.formatmonthname(theyear, themonth, 7 * (w + 1) - 1)
+        s = s.rstrip()
+        s += '\n' * l
+        s += self.formatweekheader(w).rstrip()
+        s += '\n' * l
+        for week in self.monthdays2calendar(theyear, themonth):
+            s += self.formatweek(week, w).rstrip()
+            s += '\n' * l
+        return s
+
+    def formatyear(self, theyear, w=2, l=1, c=6, m=3):
+        """
+        Returns a year's calendar as a multi-line string.
+        """
+        w = max(2, w)
+        l = max(1, l)
+        c = max(2, c)
+        colwidth = (w + 1) * 7 - 1
+        v = []
+        a = v.append
+        a(repr(theyear).center(colwidth*m+c*(m-1)).rstrip())
+        a('\n'*l)
+        header = self.formatweekheader(w)
+        for (i, row) in enumerate(self.yeardays2calendar(theyear, m)):
+            # months in this row
+            months = xrange(m*i+1, min(m*(i+1)+1, 13))
+            a('\n'*l)
+            a(formatstring((month_name[k] for k in months), colwidth, c).rstrip())
+            a('\n'*l)
+            a(formatstring((header for k in months), colwidth, c).rstrip())
+            a('\n'*l)
+            # max number of weeks for this row
+            height = max(len(cal) for cal in row)
+            for j in xrange(height):
+                weeks = []
+                for cal in row:
+                    if j >= len(cal):
+                        weeks.append('')
+                    else:
+                        weeks.append(self.formatweek(cal[j], w))
+                a(formatstring(weeks, colwidth, c).rstrip())
+                a('\n' * l)
+        return ''.join(v)
+
+    def pryear(self, theyear, w=0, l=0, c=6, m=3):
+        """Print a year's calendar."""
+        print self.formatyear(theyear, w, l, c, m)
+
+
+class HTMLCalendar(Calendar):
+    """
+    This calendar returns complete HTML pages.
+    """
+
+    # CSS classes for the day <td>s
+    cssclasses = ["mon", "tue", "wed", "thu", "fri", "sat", "sun"]
+
+    def formatday(self, day, weekday):
+        """
+        Return a day as a table cell.
+        """
+        if day == 0:
+            return '<td class="noday">&nbsp;</td>' # day outside month
+        else:
+            return '<td class="%s">%d</td>' % (self.cssclasses[weekday], day)
+
+    def formatweek(self, theweek):
+        """
+        Return a complete week as a table row.
+        """
+        s = ''.join(self.formatday(d, wd) for (d, wd) in theweek)
+        return '<tr>%s</tr>' % s
+
+    def formatweekday(self, day):
+        """
+        Return a weekday name as a table header.
+        """
+        return '<th class="%s">%s</th>' % (self.cssclasses[day], day_abbr[day])
+
+    def formatweekheader(self):
+        """
+        Return a header for a week as a table row.
+        """
+        s = ''.join(self.formatweekday(i) for i in self.iterweekdays())
+        return '<tr>%s</tr>' % s
+
+    def formatmonthname(self, theyear, themonth, withyear=True):
+        """
+        Return a month name as a table row.
+        """
+        if withyear:
+            s = '%s %s' % (month_name[themonth], theyear)
+        else:
+            s = '%s' % month_name[themonth]
+        return '<tr><th colspan="7" class="month">%s</th></tr>' % s
+
+    def formatmonth(self, theyear, themonth, withyear=True):
+        """
+        Return a formatted month as a table.
+        """
+        v = []
+        a = v.append
+        a('<table border="0" cellpadding="0" cellspacing="0" class="month">')
+        a('\n')
+        a(self.formatmonthname(theyear, themonth, withyear=withyear))
+        a('\n')
+        a(self.formatweekheader())
+        a('\n')
+        for week in self.monthdays2calendar(theyear, themonth):
+            a(self.formatweek(week))
+            a('\n')
+        a('</table>')
+        a('\n')
+        return ''.join(v)
+
+    def formatyear(self, theyear, width=3):
+        """
+        Return a formatted year as a table of tables.
+        """
+        v = []
+        a = v.append
+        width = max(width, 1)
+        a('<table border="0" cellpadding="0" cellspacing="0" class="year">')
+        a('\n')
+        a('<tr><th colspan="%d" class="year">%s</th></tr>' % (width, theyear))
+        for i in xrange(January, January+12, width):
+            # months in this row
+            months = xrange(i, min(i+width, 13))
+            a('<tr>')
+            for m in months:
+                a('<td>')
+                a(self.formatmonth(theyear, m, withyear=False))
+                a('</td>')
+            a('</tr>')
+        a('</table>')
+        return ''.join(v)
+
+    def formatyearpage(self, theyear, width=3, css='calendar.css', encoding=None):
+        """
+        Return a formatted year as a complete HTML page.
+        """
+        if encoding is None:
+            encoding = sys.getdefaultencoding()
+        v = []
+        a = v.append
+        a('<?xml version="1.0" encoding="%s"?>\n' % encoding)
+        a('<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">\n')
+        a('<html>\n')
+        a('<head>\n')
+        a('<meta http-equiv="Content-Type" content="text/html; charset=%s" />\n' % encoding)
+        if css is not None:
+            a('<link rel="stylesheet" type="text/css" href="%s" />\n' % css)
+        a('<title>Calendar for %d</title\n' % theyear)
+        a('</head>\n')
+        a('<body>\n')
+        a(self.formatyear(theyear, width))
+        a('</body>\n')
+        a('</html>\n')
+        return ''.join(v).encode(encoding)
+
+
+# Support for old module level interface
+c = TextCalendar()
+
+firstweekday = c.firstweekday
+setfirstweekday = c.setfirstweekday
+monthcalendar = c.monthdayscalendar
+prweek = c.prweek
+week = c.formatweek
+weekheader = c.formatweekheader
+prmonth = c.prmonth
+month = c.formatmonth
+calendar = c.formatyear
+prcal = c.pryear
+
+
+# Spacing of month columns for multi-column year calendar
 _colwidth = 7*3 - 1         # Amount printed by prweek()
 _spacing = 6                # Number of spaces between columns
 
-def format3c(a, b, c, colwidth=_colwidth, spacing=_spacing):
-    """Prints 3-column formatting for year calendars"""
-    print format3cstring(a, b, c, colwidth, spacing)
-
-def format3cstring(a, b, c, colwidth=_colwidth, spacing=_spacing):
-    """Returns a string formatted from 3 strings, centered within 3 columns."""
-    return (a.center(colwidth) + ' ' * spacing + b.center(colwidth) +
-            ' ' * spacing + c.center(colwidth))
-
-def prcal(year, w=0, l=0, c=_spacing):
-    """Print a year's calendar."""
-    print calendar(year, w, l, c),
-
-def calendar(year, w=0, l=0, c=_spacing):
-    """Returns a year's calendar as a multi-line string."""
-    w = max(2, w)
-    l = max(1, l)
-    c = max(2, c)
-    colwidth = (w + 1) * 7 - 1
-    s = repr(year).center(colwidth * 3 + c * 2).rstrip() + '\n' * l
-    header = weekheader(w)
-    header = format3cstring(header, header, header, colwidth, c).rstrip()
-    for q in range(January, January+12, 3):
-        s = (s + '\n' * l +
-             format3cstring(month_name[q], month_name[q+1], month_name[q+2],
-                            colwidth, c).rstrip() +
-             '\n' * l + header + '\n' * l)
-        data = []
-        height = 0
-        for amonth in range(q, q + 3):
-            cal = monthcalendar(year, amonth)
-            if len(cal) > height:
-                height = len(cal)
-            data.append(cal)
-        for i in range(height):
-            weeks = []
-            for cal in data:
-                if i >= len(cal):
-                    weeks.append('')
-                else:
-                    weeks.append(week(cal[i], w))
-            s = s + format3cstring(weeks[0], weeks[1], weeks[2],
-                                   colwidth, c).rstrip() + '\n' * l
-    return s[:-l] + '\n'
+
+def format(cols, colwidth=_colwidth, spacing=_spacing):
+    """Prints multi-column formatting for year calendars"""
+    print formatstring(cols, colwidth, spacing)
+
+
+def formatstring(cols, colwidth=_colwidth, spacing=_spacing):
+    """Returns a string formatted from n strings, centered within n columns."""
+    spacing *= ' '
+    return spacing.join(c.center(colwidth) for c in cols)
+
 
 EPOCH = 1970
 _EPOCH_ORD = datetime.date(EPOCH, 1, 1).toordinal()
 
+
 def timegm(tuple):
     """Unrelated but handy function to calculate Unix timestamp from GMT."""
     year, month, day, hour, minute, second = tuple[:6]
@@ -229,3 +520,65 @@ def timegm(tuple):
     minutes = hours*60 + minute
     seconds = minutes*60 + second
     return seconds
+
+
+def main(args):
+    import optparse
+    parser = optparse.OptionParser(usage="usage: %prog [options] [year] [month]")
+    parser.add_option("-w", "--width",
+                      dest="width", type="int", default=2,
+                      help="width of date column (default 2, text only)")
+    parser.add_option("-l", "--lines",
+                      dest="lines", type="int", default=1,
+                      help="number of lines for each week (default 1, text only)")
+    parser.add_option("-s", "--spacing",
+                      dest="spacing", type="int", default=6,
+                      help="spacing between months (default 6, text only)")
+    parser.add_option("-m", "--months",
+                      dest="months", type="int", default=3,
+                      help="months per row (default 3, text only)")
+    parser.add_option("-c", "--css",
+                      dest="css", default="calendar.css",
+                      help="CSS to use for page (html only)")
+    parser.add_option("-e", "--encoding",
+                      dest="encoding", default=None,
+                      help="Encoding to use for CSS output (html only)")
+    parser.add_option("-t", "--type",
+                      dest="type", default="text",
+                      choices=("text", "html"),
+                      help="output type (text or html)")
+
+    (options, args) = parser.parse_args(args)
+
+    if options.type == "html":
+        cal = HTMLCalendar()
+        encoding = options.encoding
+        if encoding is None:
+            encoding = sys.getdefaultencoding()
+        optdict = dict(encoding=encoding, css=options.css)
+        if len(args) == 1:
+            print cal.formatyearpage(datetime.date.today().year, **optdict)
+        elif len(args) == 2:
+            print cal.formatyearpage(int(args[1]), **optdict)
+        else:
+            parser.error("incorrect number of arguments")
+            sys.exit(1)
+    else:
+        cal = TextCalendar()
+        optdict = dict(w=options.width, l=options.lines)
+        if len(args) != 3:
+            optdict["c"] = options.spacing
+            optdict["m"] = options.months
+        if len(args) == 1:
+            print cal.formatyear(datetime.date.today().year, **optdict)
+        elif len(args) == 2:
+            print cal.formatyear(int(args[1]), **optdict)
+        elif len(args) == 3:
+            print cal.formatmonth(int(args[1]), int(args[2]), **optdict)
+        else:
+            parser.error("incorrect number of arguments")
+            sys.exit(1)
+
+
+if __name__ == "__main__":
+    main(sys.argv)
diff --git a/Lib/test/test_calendar.py b/Lib/test/test_calendar.py
index 34d365b..bd8e6b4 100644
--- a/Lib/test/test_calendar.py
+++ b/Lib/test/test_calendar.py
@@ -4,6 +4,64 @@ import unittest
 from test import test_support
 
 
+result_2004 = """
+                                  2004
+
+      January                   February                   March
+Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su
+          1  2  3  4                         1       1  2  3  4  5  6  7
+ 5  6  7  8  9 10 11       2  3  4  5  6  7  8       8  9 10 11 12 13 14
+12 13 14 15 16 17 18       9 10 11 12 13 14 15      15 16 17 18 19 20 21
+19 20 21 22 23 24 25      16 17 18 19 20 21 22      22 23 24 25 26 27 28
+26 27 28 29 30 31         23 24 25 26 27 28 29      29 30 31
+
+       April                      May                       June
+Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su
+          1  2  3  4                      1  2          1  2  3  4  5  6
+ 5  6  7  8  9 10 11       3  4  5  6  7  8  9       7  8  9 10 11 12 13
+12 13 14 15 16 17 18      10 11 12 13 14 15 16      14 15 16 17 18 19 20
+19 20 21 22 23 24 25      17 18 19 20 21 22 23      21 22 23 24 25 26 27
+26 27 28 29 30            24 25 26 27 28 29 30      28 29 30
+                          31
+
+        July                     August                  September
+Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su
+          1  2  3  4                         1             1  2  3  4  5
+ 5  6  7  8  9 10 11       2  3  4  5  6  7  8       6  7  8  9 10 11 12
+12 13 14 15 16 17 18       9 10 11 12 13 14 15      13 14 15 16 17 18 19
+19 20 21 22 23 24 25      16 17 18 19 20 21 22      20 21 22 23 24 25 26
+26 27 28 29 30 31         23 24 25 26 27 28 29      27 28 29 30
+                          30 31
+
+      October                   November                  December
+Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su
+             1  2  3       1  2  3  4  5  6  7             1  2  3  4  5
+ 4  5  6  7  8  9 10       8  9 10 11 12 13 14       6  7  8  9 10 11 12
+11 12 13 14 15 16 17      15 16 17 18 19 20 21      13 14 15 16 17 18 19
+18 19 20 21 22 23 24      22 23 24 25 26 27 28      20 21 22 23 24 25 26
+25 26 27 28 29 30 31      29 30                     27 28 29 30 31
+"""
+
+
+class OutputTestCase(unittest.TestCase):
+    def normalize_calendar(self, s):
+        def neitherspacenordigit(c):
+            return not c.isspace() and not c.isdigit()
+
+        lines = []
+        for line in s.splitlines(False):
+            # Drop texts, as they are locale dependent
+            if line and not filter(neitherspacenordigit, line):
+                lines.append(line)
+        return lines
+
+    def test_output(self):
+        self.assertEqual(
+            self.normalize_calendar(calendar.calendar(2004)),
+            self.normalize_calendar(result_2004)
+        )
+
+
 class CalendarTestCase(unittest.TestCase):
     def test_isleap(self):
         # Make sure that the return is right for a few years, and
@@ -72,57 +130,57 @@ class MondayTestCase(MonthCalendarTestCase):
     firstweekday = calendar.MONDAY
 
     def test_february(self):
-        # A 28-day february starting of monday (7+7+7+7 days)
+        # A 28-day february starting on monday (7+7+7+7 days)
         self.check_weeks(1999, 2, (7, 7, 7, 7))
 
-        # A 28-day february starting of tuesday (6+7+7+7+1 days)
+        # A 28-day february starting on tuesday (6+7+7+7+1 days)
         self.check_weeks(2005, 2, (6, 7, 7, 7, 1))
 
-        # A 28-day february starting of sunday (1+7+7+7+6 days)
+        # A 28-day february starting on sunday (1+7+7+7+6 days)
         self.check_weeks(1987, 2, (1, 7, 7, 7, 6))
 
-        # A 29-day february starting of monday (7+7+7+7+1 days)
+        # A 29-day february starting on monday (7+7+7+7+1 days)
         self.check_weeks(1988, 2, (7, 7, 7, 7, 1))
 
-        # A 29-day february starting of tuesday (6+7+7+7+2 days)
+        # A 29-day february starting on tuesday (6+7+7+7+2 days)
         self.check_weeks(1972, 2, (6, 7, 7, 7, 2))
 
-        # A 29-day february starting of sunday (1+7+7+7+7 days)
+        # A 29-day february starting on sunday (1+7+7+7+7 days)
         self.check_weeks(2004, 2, (1, 7, 7, 7, 7))
 
     def test_april(self):
-        # A 30-day april starting of monday (7+7+7+7+2 days)
+        # A 30-day april starting on monday (7+7+7+7+2 days)
         self.check_weeks(1935, 4, (7, 7, 7, 7, 2))
 
-        # A 30-day april starting of tuesday (6+7+7+7+3 days)
+        # A 30-day april starting on tuesday (6+7+7+7+3 days)
         self.check_weeks(1975, 4, (6, 7, 7, 7, 3))
 
-        # A 30-day april starting of sunday (1+7+7+7+7+1 days)
+        # A 30-day april starting on sunday (1+7+7+7+7+1 days)
         self.check_weeks(1945, 4, (1, 7, 7, 7, 7, 1))
 
-        # A 30-day april starting of saturday (2+7+7+7+7 days)
+        # A 30-day april starting on saturday (2+7+7+7+7 days)
         self.check_weeks(1995, 4, (2, 7, 7, 7, 7))
 
-        # A 30-day april starting of friday (3+7+7+7+6 days)
+        # A 30-day april starting on friday (3+7+7+7+6 days)
         self.check_weeks(1994, 4, (3, 7, 7, 7, 6))
 
     def test_december(self):
-        # A 31-day december starting of monday (7+7+7+7+3 days)
+        # A 31-day december starting on monday (7+7+7+7+3 days)
         self.check_weeks(1980, 12, (7, 7, 7, 7, 3))
 
-        # A 31-day december starting of tuesday (6+7+7+7+4 days)
+        # A 31-day december starting on tuesday (6+7+7+7+4 days)
         self.check_weeks(1987, 12, (6, 7, 7, 7, 4))
 
-        # A 31-day december starting of sunday (1+7+7+7+7+2 days)
+        # A 31-day december starting on sunday (1+7+7+7+7+2 days)
         self.check_weeks(1968, 12, (1, 7, 7, 7, 7, 2))
 
-        # A 31-day december starting of thursday (4+7+7+7+6 days)
+        # A 31-day december starting on thursday (4+7+7+7+6 days)
         self.check_weeks(1988, 12, (4, 7, 7, 7, 6))
 
-        # A 31-day december starting of friday (3+7+7+7+7 days)
+        # A 31-day december starting on friday (3+7+7+7+7 days)
         self.check_weeks(2017, 12, (3, 7, 7, 7, 7))
 
-        # A 31-day december starting of saturday (2+7+7+7+7+1 days)
+        # A 31-day december starting on saturday (2+7+7+7+7+1 days)
         self.check_weeks(2068, 12, (2, 7, 7, 7, 7, 1))
 
 
@@ -130,62 +188,63 @@ class SundayTestCase(MonthCalendarTestCase):
     firstweekday = calendar.SUNDAY
 
     def test_february(self):
-        # A 28-day february starting of sunday (7+7+7+7 days)
+        # A 28-day february starting on sunday (7+7+7+7 days)
         self.check_weeks(2009, 2, (7, 7, 7, 7))
 
-        # A 28-day february starting of monday (6+7+7+7+1 days)
+        # A 28-day february starting on monday (6+7+7+7+1 days)
         self.check_weeks(1999, 2, (6, 7, 7, 7, 1))
 
-        # A 28-day february starting of saturday (1+7+7+7+6 days)
+        # A 28-day february starting on saturday (1+7+7+7+6 days)
         self.check_weeks(1997, 2, (1, 7, 7, 7, 6))
 
-        # A 29-day february starting of sunday (7+7+7+7+1 days)
+        # A 29-day february starting on sunday (7+7+7+7+1 days)
         self.check_weeks(2004, 2, (7, 7, 7, 7, 1))
 
-        # A 29-day february starting of monday (6+7+7+7+2 days)
+        # A 29-day february starting on monday (6+7+7+7+2 days)
         self.check_weeks(1960, 2, (6, 7, 7, 7, 2))
 
-        # A 29-day february starting of saturday (1+7+7+7+7 days)
+        # A 29-day february starting on saturday (1+7+7+7+7 days)
         self.check_weeks(1964, 2, (1, 7, 7, 7, 7))
 
     def test_april(self):
-        # A 30-day april starting of sunday (7+7+7+7+2 days)
+        # A 30-day april starting on sunday (7+7+7+7+2 days)
         self.check_weeks(1923, 4, (7, 7, 7, 7, 2))
 
-        # A 30-day april starting of monday (6+7+7+7+3 days)
+        # A 30-day april starting on monday (6+7+7+7+3 days)
         self.check_weeks(1918, 4, (6, 7, 7, 7, 3))
 
-        # A 30-day april starting of saturday (1+7+7+7+7+1 days)
+        # A 30-day april starting on saturday (1+7+7+7+7+1 days)
         self.check_weeks(1950, 4, (1, 7, 7, 7, 7, 1))
 
-        # A 30-day april starting of friday (2+7+7+7+7 days)
+        # A 30-day april starting on friday (2+7+7+7+7 days)
         self.check_weeks(1960, 4, (2, 7, 7, 7, 7))
 
-        # A 30-day april starting of thursday (3+7+7+7+6 days)
+        # A 30-day april starting on thursday (3+7+7+7+6 days)
         self.check_weeks(1909, 4, (3, 7, 7, 7, 6))
 
     def test_december(self):
-        # A 31-day december starting of sunday (7+7+7+7+3 days)
+        # A 31-day december starting on sunday (7+7+7+7+3 days)
         self.check_weeks(2080, 12, (7, 7, 7, 7, 3))
 
-        # A 31-day december starting of monday (6+7+7+7+4 days)
+        # A 31-day december starting on monday (6+7+7+7+4 days)
         self.check_weeks(1941, 12, (6, 7, 7, 7, 4))
 
-        # A 31-day december starting of saturday (1+7+7+7+7+2 days)
+        # A 31-day december starting on saturday (1+7+7+7+7+2 days)
         self.check_weeks(1923, 12, (1, 7, 7, 7, 7, 2))
 
-        # A 31-day december starting of wednesday (4+7+7+7+6 days)
+        # A 31-day december starting on wednesday (4+7+7+7+6 days)
         self.check_weeks(1948, 12, (4, 7, 7, 7, 6))
 
-        # A 31-day december starting of thursday (3+7+7+7+7 days)
+        # A 31-day december starting on thursday (3+7+7+7+7 days)
         self.check_weeks(1927, 12, (3, 7, 7, 7, 7))
 
-        # A 31-day december starting of friday (2+7+7+7+7+1 days)
+        # A 31-day december starting on friday (2+7+7+7+7+1 days)
         self.check_weeks(1995, 12, (2, 7, 7, 7, 7, 1))
 
 
 def test_main():
     test_support.run_unittest(
+        OutputTestCase,
         CalendarTestCase,
         MondayTestCase,
         SundayTestCase
diff --git a/Misc/NEWS b/Misc/NEWS
index 08b7714..38a608b 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -895,6 +895,10 @@ Library
 - Patch #1413711: Certain patterns of differences were making difflib
   touch the recursion limit.
 
+- Bug #947906: An object oriented interface has been added to the calendar
+  module. It's possible to generate HTML calendar now and the module can be
+  called as a script (e.g. via ``python -mcalendar``).
+
 Build
 -----