Lib/calendar.py

"""Calendar printing functions"""

# Revision 2: uses funtions from built-in time module

# Import functions and variables from time module
from time import localtime, mktime

# Exception raised for bad input (with string parameter for details)
error = ValueError

# Note when comparing these calendars to the ones printed by cal(1):
# My calendars have Monday as the first day of the week, and Sunday as
# the last!  (I believe this is the European convention.)

# Constants for months referenced later
January = 1
February = 2

# Number of days per month (except for February in leap years)
mdays = [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

# Full and abbreviated names of weekdays
day_name = ['Monday', 'Tuesday', 'Wednesday', 'Thursday',
            'Friday', 'Saturday', 'Sunday']
day_abbr = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']

# Full and abbreviated names of months (1-based arrays!!!)
month_name = ['', 'January', 'February', 'March', 'April',
              'May', 'June', 'July', 'August',
              'September', 'October',  'November', 'December']
month_abbr = ['   ', 'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
              'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']

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 and no funny (non-leap century) years."""
    return (y2+3)/4 - (y1+3)/4

def weekday(year, month, day):
    """Return weekday (0-6 ~ Mon-Sun) for year (1970-...), month (1-12), day (1-31)."""
    secs = mktime((year, month, day, 0, 0, 0, 0, 0, 0))
    tuple = localtime(secs)
    return tuple[6]

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'
    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 = 1 - day1
    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

_mc_cache = {}
def monthcalendar(year, month):
    """Caching interface to _monthcalendar."""
    key = (year, month)
    if _mc_cache.has_key(key):
        return _mc_cache[key]
    else:
        _mc_cache[key] = ret = _monthcalendar(year, month)
        return ret

def _center(str, width):
    """Center a string in a field."""
    n = width - len(str)
    if n <= 0: return str
    return ' '*((n+1)/2) + str + ' '*((n)/2)

# XXX The following code knows that print separates items with space!

def prweek(week, width):
    """Print a single week (no newline)."""
    for day in week:
        if day == 0: s = ''
        else: s = `day`
        print _center(s, width),

def weekheader(width):
    """Return a header for a week."""
    str = ''
    if width >= 9: names = day_name
    else: names = day_abbr
    for i in range(7):
        if str: str = str + ' '
        str = str + _center(names[i%7][:width], width)
    return str

def prmonth(year, month, w = 0, l = 0):
    """Print a month's calendar."""
    w = max(2, w)
    l = max(1, l)
    print _center(month_name[month] + ' ' + `year`, 7*(w+1) - 1),
    print '\n'*l,
    print weekheader(w),
    print '\n'*l,
    for week in monthcalendar(year, month):
        prweek(week, w)
        print '\n'*l,

# Spacing of month columns
_colwidth = 7*3 - 1         # Amount printed by prweek()
_spacing = ' '*4            # Spaces between columns

def format3c(a, b, c):
    """3-column formatting for year calendars"""
    print _center(a, _colwidth),
    print _spacing,
    print _center(b, _colwidth),
    print _spacing,
    print _center(c, _colwidth)

def prcal(year):
    """Print a year's calendar."""
    header = weekheader(2)
    format3c('', `year`, '')
    for q in range(January, January+12, 3):
        print
        format3c(month_name[q], month_name[q+1], month_name[q+2])
        format3c(header, header, header)
        data = []
        height = 0
        for month in range(q, q+3):
            cal = monthcalendar(year, month)
            if len(cal) > height: height = len(cal)
            data.append(cal)
        for i in range(height):
            for cal in data:
                if i >= len(cal):
                    print ' '*_colwidth,
                else:
                    prweek(cal[i], 2)
                print _spacing,
            print

EPOCH = 1970
def timegm(tuple):
    """Unrelated but handy function to calculate Unix timestamp from GMT."""
    year, month, day, hour, minute, second = tuple[:6]
    assert year >= EPOCH
    assert 1 <= month <= 12
    days = 365*(year-EPOCH) + leapdays(EPOCH, year)
    for i in range(1, month):
        days = days + mdays[i]
    if month > 2 and isleap(year):
        days = days + 1
    days = days + day - 1
    hours = days*24 + hour
    minutes = hours*60 + minute
    seconds = minutes*60 + second
    return seconds