# # Copyright (c) 2009, 2010 Tom Keffer # # See the file LICENSE.txt for your full rights. # # $Revision$ # $Author$ # $Date$ # """Various handy utilities that don't belong anywhere else.""" import StringIO import calendar import datetime import math import syslog import time import traceback import configobj import Sun def convertToFloat(seq): """Convert a sequence with strings to floats, honoring 'Nones'""" if seq is None: return None res = [None if s in ('None', 'none') else float(s) for s in seq] return res def accumulateLeaves(d): """Merges leaf options above a ConfigObj section with itself, accumulating the results. This routine is useful for specifying defaults near the root node, then having them overridden in the leaf nodes of a ConfigObj. d: instance of a configobj.Section (i.e., a section of a ConfigObj) """ # Use recursion. If I am the root object, then there is nothing above # me to accumulate. Start with a virgin ConfigObj if d.parent is d : cum_dict = configobj.ConfigObj() else : # Otherwise, recursively accumulate scalars above me cum_dict = accumulateLeaves(d.parent) # Now merge my scalars into the results: merge_dict = {} for k in d.scalars : merge_dict[k] = d[k] cum_dict.merge(merge_dict) return cum_dict def option_as_list(option): if option is None: return None if hasattr(option, '__iter__'): return option return [option] def stampgen(startstamp, stopstamp, interval): """Generator function yielding a sequence of timestamps, spaced interval apart. The sequence will fall on the same local time boundary as startstamp. Example: >>> startstamp = 1236560400 >>> print timestamp_to_string(startstamp) 2009-03-08 18:00:00 PDT (1236560400) >>> stopstamp = 1236607200 >>> print timestamp_to_string(stopstamp) 2009-03-09 07:00:00 PDT (1236607200) >>> for stamp in stampgen(startstamp, stopstamp, 10800): ... print timestamp_to_string(stamp) 2009-03-08 18:00:00 PDT (1236560400) 2009-03-08 21:00:00 PDT (1236571200) 2009-03-09 00:00:00 PDT (1236582000) 2009-03-09 03:00:00 PDT (1236592800) 2009-03-09 06:00:00 PDT (1236603600) Note that DST started in the middle of the sequence and that therefore the actual time deltas between stamps is not necessarily 3 hours. startstamp: The start of the sequence in unix epoch time. stopstamp: The end of the sequence in unix epoch time. interval: The time length of an interval in seconds. yields a sequence of timestamps between startstamp and endstamp, inclusive. """ dt = datetime.datetime.fromtimestamp(startstamp) stop_dt = datetime.datetime.fromtimestamp(stopstamp) if interval == 365.25 / 12 * 24 * 3600 : # Interval is a nominal month. This algorithm is # necessary because not all months have the same length. while dt <= stop_dt : t_tuple = dt.timetuple() yield time.mktime(t_tuple) year = t_tuple[0] month = t_tuple[1] month += 1 if month > 12 : month -= 12 year += 1 dt = dt.replace(year=year, month=month) else : # This rather complicated algorithm is necessary (rather than just # doing some time stamp arithmetic) because of the possibility that DST # changes in the middle of an interval delta = datetime.timedelta(seconds=interval) while dt <= stop_dt : yield int(time.mktime(dt.timetuple())) dt += delta def intervalgen(start_ts, stop_ts, interval): """Generator function yielding a sequence of time intervals. Yields a sequence of intervals. First interval is (start_ts, start_ts+interval), second is (start_ts+interval, start_ts+2*interval), etc. The last interval will end at or before stop_ts. It is up to the consumer to interpret whether the end points of any given interval is inclusive or exclusive to the interval. Example: >>> startstamp = 1236560400 >>> print timestamp_to_string(startstamp) 2009-03-08 18:00:00 PDT (1236560400) >>> stopstamp = 1236607200 >>> print timestamp_to_string(stopstamp) 2009-03-09 07:00:00 PDT (1236607200) >>> for start,stop in intervalgen(startstamp, stopstamp, 10800): ... print timestamp_to_string(start), timestamp_to_string(stop) 2009-03-08 18:00:00 PDT (1236560400) 2009-03-08 21:00:00 PDT (1236571200) 2009-03-08 21:00:00 PDT (1236571200) 2009-03-09 00:00:00 PDT (1236582000) 2009-03-09 00:00:00 PDT (1236582000) 2009-03-09 03:00:00 PDT (1236592800) 2009-03-09 03:00:00 PDT (1236592800) 2009-03-09 06:00:00 PDT (1236603600) 2009-03-09 06:00:00 PDT (1236603600) 2009-03-09 07:00:00 PDT (1236607200) start_ts: The start of the first interval in unix epoch time. stop_ts: The end of the last interval will be equal to or less than this. In unix epoch time. interval: The time length of an interval in seconds. yields: A sequence of 2-tuples. First value is start of the interval, second is the end. Both the start and end will be on the same time boundary as start_ts""" dt1 = datetime.datetime.fromtimestamp(start_ts) stop_dt = datetime.datetime.fromtimestamp(stop_ts) if interval == 365.25 / 12 * 24 * 3600 : # Interval is a nominal month. This algorithm is # necessary because not all months have the same length. while dt1 < stop_dt : t_tuple = dt1.timetuple() year = t_tuple[0] month = t_tuple[1] month += 1 if month > 12 : month -= 12 year += 1 dt2 = min(dt1.replace(year=year, month=month), stop_dt) stamp1 = time.mktime(t_tuple) stamp2 = time.mktime(dt2.timetuple()) yield (stamp1, stamp2) dt1 = dt2 else : # This rather complicated algorithm is necessary (rather than just # doing some time stamp arithmetic) because of the possibility that DST # changes in the middle of an interval delta = datetime.timedelta(seconds=interval) while dt1 < stop_dt : dt2 = min(dt1 + delta, stop_dt) stamp1 = time.mktime(dt1.timetuple()) stamp2 = time.mktime(dt2.timetuple()) yield (stamp1, stamp2) dt1 = dt2 def startOfInterval(time_ts, interval, grace=1): """Find the start time of an interval. This algorithm assumes the day is divided up into intervals of 'interval' length. Given a timestamp, it figures out which interval it lies in, returning the start time. Examples (human readable times shown instead of timestamps): time_ts interval returns 01:57:35 300 01:55:00 01:57:35 600 01:50:00 01:57:35 900 01:45:00 01:57:35 3600 01:00:00 01:57:35 7200 00:00:00 01:00:00 300 00:55:00 time_ts: A timestamp. The start of the interval containing this timestamp will be returned. interval: An interval length in seconds. grace: A time this many seconds into an interval is still included in the last interval. Set to zero to have an inclusive start of an interval. [Optional. Default is 1 second.] Returns: A timestamp with the start of the interval.""" interval_m = interval/60 interval_h = interval/3600 time_tt = time.localtime(time_ts - grace) m = time_tt.tm_min // interval_m * interval_m h = time_tt.tm_hour // interval_h * interval_h if interval_h > 1 else time_tt.tm_hour # Replace the hour, minute, and seconds with the start of the interval. # Everything else gets retained: start_interval_ts = time.mktime((time_tt.tm_year, time_tt.tm_mon, time_tt.tm_mday, h, m, 0, 0, 0, time_tt.tm_isdst)) return int(start_interval_ts) def _ord_to_ts(_ord): d = datetime.date.fromordinal(_ord) t = int(time.mktime(d.timetuple())) return t #=============================================================================== # What follows is a bunch of "time span" routines. Generally, time spans # are used when start and stop times fall on calendar boundaries # such as days, months, years. So, it makes sense to talk of "daySpans", # "weekSpans", etc. They are generally not used between two random times. #=============================================================================== class TimeSpan(object): ''' Represents a time span, exclusive on the left, inclusive on the right. ''' def __init__(self, start_ts, stop_ts): ''' Initialize a new instance of TimeSpan to the interval start_ts, stop_ts. start_ts: The starting time stamp of the interval. stop_ts: The stopping time stamp of the interval ''' self.start = int(start_ts) self.stop = int(stop_ts) if self.start > self.stop: raise ValueError, "start time (%d) is greater than stop time (%d)" % (self.start, self.stop) def includesArchiveTime(self, timestamp): """ Returns True if the span includes the time timestamp, otherwise False. timestamp: The timestamp to be tested. """ return self.start < timestamp <= self.stop def includes(self, span): return self.start <= span.start <= self.stop and self.start <= span.stop <= self.stop def __eq__(self, other): return self.start == other.start and self.stop == other.stop def __str__(self): return "[%s -> %s]" % (timestamp_to_string(self.start), timestamp_to_string(self.stop)) def __hash__(self): return hash(self.start) ^ hash(self.stop) def __cmp__(self, other): if self.start < other.start : return - 1 return 0 if self.start == other.start else 1 def archiveDaySpan(time_ts, grace=1): """Returns a TimeSpan representing a day that includes a given time. Midnight is considered to actually belong in the previous day if grace is greater than zero. Examples: (Assume grace is 1; printed times are given below, but the variables are actually in unix epoch timestamps) 2007-12-3 18:12:05 returns (2007-12-3 00:00:00 to 2007-12-4 00:00:00) 2007-12-3 00:00:00 returns (2007-12-2 00:00:00 to 2007-12-3 00:00:00) 2007-12-3 00:00:01 returns (2007-12-3 00:00:00 to 2007-12-4 00:00:00) time_ts: The day will include this timestamp. grace: This many seconds past midnight marks the start of the next day. Set to zero to have midnight be included in the following day. [Optional. Default is 1 second.] returns: A TimeSpan object one day long that contains time_ts. It will begin and end at midnight. """ if time_ts is None: return None time_ts -= grace _day_date = datetime.date.fromtimestamp(time_ts) _day_ord = _day_date.toordinal() return TimeSpan(_ord_to_ts(_day_ord), _ord_to_ts(_day_ord + 1)) def archiveWeekSpan(time_ts, startOfWeek=6, grace=1): """Returns a TimeSpan representing a week that includes a given time. The time at midnight at the end of the week is considered to actually belong in the previous week. time_ts: The week will include this timestamp. startOfWeek: The start of the week (0=Monday, 1=Tues, ..., 6 = Sun). grace: This many seconds past midnight marks the start of the next week. Set to zero to have midnight be included in the following week. [Optional. Default is 1 second.] returns: A TimeSpan object one week long that contains time_ts. It will start at midnight of the day considered the start of the week, and be one week long. """ if time_ts is None: return None time_ts -= grace _day_date = datetime.date.fromtimestamp(time_ts) _day_of_week = _day_date.weekday() _delta = _day_of_week - startOfWeek if _delta < 0: _delta += 7 _sunday_date = _day_date - datetime.timedelta(days=_delta) _next_sunday_date = _sunday_date + datetime.timedelta(days=7) return TimeSpan(int(time.mktime(_sunday_date.timetuple())), int(time.mktime(_next_sunday_date.timetuple()))) def archiveMonthSpan(time_ts, grace=1): """Returns a TimeSpan representing a month that includes a given time. Midnight of the 1st of the month is considered to actually belong in the previous month. time_ts: The month will include this timestamp. grace: This many seconds past midnight marks the start of the next month. Set to zero to have midnight be included in the following month. [Optional. Default is 1 second.] returns: A TimeSpan object one month long that contains time_ts. It will start at midnight of the start of the month, and end at midnight of the start of the next month. """ if time_ts is None: return None time_ts -= grace _day_date = datetime.date.fromtimestamp(time_ts) _month_date = _day_date.replace(day=1) _yr = _month_date.year _mo = _month_date.month + 1 if _mo == 13: _mo = 1 _yr += 1 _next_month_date = datetime.date(_yr, _mo, 1) return TimeSpan(int(time.mktime(_month_date.timetuple())), int(time.mktime(_next_month_date.timetuple()))) def archiveYearSpan(time_ts, grace=1): """Returns a TimeSpan representing a year that includes a given time. Midnight of the 1st of the January is considered to actually belong in the previous year. time_ts: The year will include this timestamp. grace: This many seconds past midnight marks the start of the next year. Set to zero to have midnight be included in the following year. [Optional. Default is 1 second.] returns: A TimeSpan object one year long that contains time_ts. It will begin and end at midnight 1-Jan. """ if time_ts is None: return None time_ts -= grace _day_date = datetime.date.fromtimestamp(time_ts) return TimeSpan(int(time.mktime((_day_date.year, 1, 1, 0, 0, 0, 0, 0, -1))), int(time.mktime((_day_date.year + 1, 1, 1, 0, 0, 0, 0, 0, -1)))) def archiveRainYearSpan(time_ts, sory_mon, grace=1): """Returns a TimeSpan representing a rain year that includes a given time. Midnight of the 1st of the month starting the rain year is considered to actually belong in the previous rain year. time_ts: The rain year will include this timestamp. sory_mon: The month the rain year starts. grace: This many seconds past midnight marks the start of the next rain year. Set to zero to have midnight be included in the following rain year. [Optional. Default is 1 second.] returns: A TimeSpan object one year long that contains time_ts. It will begin on the 1st of the month that starts the rain year. """ if time_ts is None: return None time_ts -= grace _day_date = datetime.date.fromtimestamp(time_ts) _year = _day_date.year if _day_date.month >= sory_mon else _day_date.year - 1 return TimeSpan(int(time.mktime((_year, sory_mon, 1, 0, 0, 0, 0, 0, -1))), int(time.mktime((_year + 1, sory_mon, 1, 0, 0, 0, 0, 0, -1)))) def genDaySpans(start_ts, stop_ts): """Generator function that generates start/stop of days in an inclusive range. Example: >>> start_ts = 1204796460 >>> stop_ts = 1205265720 >>> print timestamp_to_string(start_ts) 2008-03-06 01:41:00 PST (1204796460) >>> print timestamp_to_string(stop_ts) 2008-03-11 13:02:00 PDT (1205265720) >>> for span in genDaySpans(start_ts, stop_ts): ... print span [2008-03-06 00:00:00 PST (1204790400) -> 2008-03-07 00:00:00 PST (1204876800)] [2008-03-07 00:00:00 PST (1204876800) -> 2008-03-08 00:00:00 PST (1204963200)] [2008-03-08 00:00:00 PST (1204963200) -> 2008-03-09 00:00:00 PST (1205049600)] [2008-03-09 00:00:00 PST (1205049600) -> 2008-03-10 00:00:00 PDT (1205132400)] [2008-03-10 00:00:00 PDT (1205132400) -> 2008-03-11 00:00:00 PDT (1205218800)] [2008-03-11 00:00:00 PDT (1205218800) -> 2008-03-12 00:00:00 PDT (1205305200)] Note that a daylight savings time change happened 8 March 2009. start_ts: A time stamp somewhere in the first day. stop_ts: A time stamp somewhere in the last day. yields: Instance of TimeSpan, where the start is the time stamp of the start of the day, the stop is the time stamp of the start of the next day. """ _start_dt = datetime.datetime.fromtimestamp(start_ts) _stop_dt = datetime.datetime.fromtimestamp(stop_ts) _start_ord = _start_dt.toordinal() _stop_ord = _stop_dt.toordinal() if (_stop_dt.hour, _stop_dt.minute, _stop_dt.second) == (0, 0, 0): _stop_ord -= 1 for _ord in range(_start_ord, _stop_ord + 1): yield TimeSpan(_ord_to_ts(_ord), _ord_to_ts(_ord + 1)) def genMonthSpans(start_ts, stop_ts): """Generator function that generates start/stop of months in an inclusive range. Example: >>> start_ts = 1196705700 >>> stop_ts = 1206101100 >>> print "start time is", timestamp_to_string(start_ts) start time is 2007-12-03 10:15:00 PST (1196705700) >>> print "stop time is ", timestamp_to_string(stop_ts) stop time is 2008-03-21 05:05:00 PDT (1206101100) >>> for span in genMonthSpans(start_ts, stop_ts): ... print span [2007-12-01 00:00:00 PST (1196496000) -> 2008-01-01 00:00:00 PST (1199174400)] [2008-01-01 00:00:00 PST (1199174400) -> 2008-02-01 00:00:00 PST (1201852800)] [2008-02-01 00:00:00 PST (1201852800) -> 2008-03-01 00:00:00 PST (1204358400)] [2008-03-01 00:00:00 PST (1204358400) -> 2008-04-01 00:00:00 PDT (1207033200)] Note that a daylight savings time change happened 8 March 2009. start_ts: A time stamp somewhere in the first month. stop_ts: A time stamp somewhere in the last month. yields: Instance of TimeSpan, where the start is the time stamp of the start of the month, the stop is the time stamp of the start of the next month. """ if None in (start_ts, stop_ts): return _start_dt = datetime.date.fromtimestamp(start_ts) _stop_date = datetime.datetime.fromtimestamp(stop_ts) _start_month = 12 * _start_dt.year + _start_dt.month _stop_month = 12 * _stop_date.year + _stop_date.month if (_stop_date.day, _stop_date.hour, _stop_date.minute, _stop_date.second) == (1, 0, 0, 0): _stop_month -= 1 for month in range(_start_month, _stop_month + 1): _this_yr, _this_mo = divmod(month, 12) _next_yr, _next_mo = divmod(month + 1, 12) yield TimeSpan(time.mktime((_this_yr, _this_mo, 1, 0, 0, 0, 0, 0, -1)), time.mktime((_next_yr, _next_mo, 1, 0, 0, 0, 0, 0, -1))) def genYearSpans(start_ts, stop_ts): if None in (start_ts, stop_ts): return _start_date = datetime.date.fromtimestamp(start_ts) _stop_dt = datetime.datetime.fromtimestamp(stop_ts) _start_year = _start_date.year _stop_year = _stop_dt.year if(_stop_dt.month, _stop_dt.day, _stop_dt.hour, _stop_dt.minute, _stop_dt.second) == (1, 1, 0, 0, 0): _stop_year -= 1 for year in range(_start_year, _stop_year + 1): yield TimeSpan(time.mktime((year, 1, 1, 0, 0, 0, 0, 0, -1)), time.mktime((year + 1, 1, 1, 0, 0, 0, 0, 0, -1))) def startOfDay(time_ts): """Calculate the unix epoch time for the start of a (local time) day. time_ts: A timestamp somewhere in the day for which the start-of-day is desired. returns: The timestamp for the start-of-day (00:00) in unix epoch time. """ _time_tt = time.localtime(time_ts) _bod_ts = time.mktime((_time_tt.tm_year, _time_tt.tm_mon, _time_tt.tm_mday, 0, 0, 0, 0, 0, -1)) return int(_bod_ts) def startOfArchiveDay(time_ts, grace=1): """Given an archive time stamp, calculate its start of day. similar to startOfDay(), except that an archive stamped at midnight actually belongs to the *previous* day. time_ts: A timestamp somewhere in the day for which the start-of-day is desired. grace: The number of seconds past midnight when the following day is considered to start [Optional. Default is 1 second] returns: The timestamp for the start-of-day (00:00) in unix epoch time.""" return startOfDay(time_ts - grace) def getDayNightTransitions(start_ts, end_ts, lat, lon): """Return the day-night transitions between the start and end times. start_ts: A timestamp indicating the beginning of the period end_ts: A timestamp indicating the end of the period returns: indication of whether the period from start to first transition is day or night, plus array of transitions. """ first = 'day' values = [] for t in range(start_ts, end_ts, 3600*24): x = startOfDay(t) + 7200 # avoid dst issues x_tt = time.gmtime(x) y, m, d = x_tt[:3] (sunrise_utc, sunset_utc) = Sun.sunRiseSet(y, m, d, lon, lat) # The above function returns its results in UTC hours. Convert # to a local time tuple, then to a timestamp. sunrise_tt = utc_to_local_tt(y, m, d, sunrise_utc) sunset_tt = utc_to_local_tt(y, m, d, sunset_utc) sunrise_ts = time.mktime(sunrise_tt) sunset_ts = time.mktime(sunset_tt) if start_ts < sunrise_ts < end_ts: values.append(sunrise_ts) if start_ts < sunset_ts < end_ts: values.append(sunset_ts) if t == start_ts and (start_ts < sunrise_ts or sunset_ts < start_ts): first = 'night' return first, values def secs_to_string(secs): """Convert seconds to a string with days, hours, and minutes""" str_list = [] for (label, interval) in (('day', 86400), ('hour', 3600), ('minute', 60)): amt = int(secs / interval) plural = '' if amt == 1 else 's' str_list.append("%d %s%s" % (amt, label, plural)) secs %= interval ans = ', '.join(str_list) return ans def timestamp_to_string(ts): """Return a string formatted from the timestamp Example: >>> print timestamp_to_string(1196705700) 2007-12-03 10:15:00 PST (1196705700) >>> print timestamp_to_string(None) ******* N/A ******* ( N/A ) """ if ts: return "%s (%d)" % (time.strftime("%Y-%m-%d %H:%M:%S %Z", time.localtime(ts)), ts) else: return "******* N/A ******* ( N/A )" def timestamp_to_gmtime(ts): """Return a string formatted for GMT >>> print timestamp_to_gmtime(1196705700) 2007-12-03 18:15:00 UTC (1196705700) >>> print timestamp_to_gmtime(None) ******* N/A ******* ( N/A ) """ if ts: return "%s (%d)" % (time.strftime("%Y-%m-%d %H:%M:%S UTC", time.gmtime(ts)), ts) else: return "******* N/A ******* ( N/A )" def utcdatetime_to_timestamp(dt): """Convert from a datetime object holding a UTC time, to a unix timestamp. dt: An instance of datetime.datetime holding the time in UTC. Returns: A timestamp Example (using 17-Jan-2011 19:21:05 UTC): >>> dt_utc = datetime.datetime(2011, 1, 17, 19, 21, 5) >>> ts = utcdatetime_to_timestamp(dt_utc) >>> print "%s UTC (unix epoch time %.1f)" % (time.asctime(time.gmtime(ts)), ts) Mon Jan 17 19:21:05 2011 UTC (unix epoch time 1295292065.0) """ # Amazingly, Python offers no easy way to do this. Here's the best # hack I can some up with: return time.mktime(dt.utctimetuple()) - time.timezone def utc_to_local_tt(y, m, d, hrs_utc): """Converts from a UTC time to a local time. y,m,d: The year, month, day for which the conversion is desired. hrs_tc: Floating point number with the number of hours since midnight in UTC. Returns: A timetuple with the local time.""" # Construct a time tuple with the time at midnight, UTC: daystart_utc_tt = (y,m,d,0,0,0,0,0,-1) # Convert the time tuple to a time stamp and add on the number of seconds since midnight: time_ts = int(calendar.timegm(daystart_utc_tt) + hrs_utc * 3600.0 + 0.5) # Convert to local time: time_local_tt = time.localtime(time_ts) return time_local_tt def latlon_string(ll, hemi, which): """Decimal degrees into a string for degrees, and one for minutes.""" labs = abs(ll) (frac, deg) = math.modf(labs) minutes = frac * 60.0 return (("%02d" if which == 'lat' else "%03d") % (deg,), "%05.2f" % (minutes,), hemi[0] if ll >= 0 else hemi[1]) def utf8_to_latin1(instring): """Convert from UTF-8 to Latin-1 encoding.""" return unicode(instring, "utf8").encode("latin1") def log_traceback(prefix=''): """Log the stack traceback into syslog.""" sfd = StringIO.StringIO() traceback.print_exc(file=sfd) sfd.seek(0) for line in sfd: syslog.syslog(syslog.LOG_INFO, prefix + line) del sfd def _get_object(module_class): """Given a path to a class, instantiates an instance of the class with the given args and returns it.""" # Split the path into its parts parts = module_class.split('.') # Strip off the classname: module = '.'.join(parts[:-1]) # Import the top level module mod = __import__(module) # Then recursively work down from the top level module to the class name: for part in parts[1:]: mod = getattr(mod, part) return mod class GenWithPeek(object): """Generator object which allows a peek at the next object to be returned. Sometimes Python solves a complicated problem with such elegance! This is one of them. Example of usage: >>> # Define a generator function: >>> def genfunc(N): ... for i in range(N): ... yield i >>> >>> # Now wrap it with the GenWithPeek object: >>> g_with_peek = GenWithPeek(genfunc(5)) >>> # We can iterate through the object as normal: >>> for i in g_with_peek: ... print i ... # Every second object, let's take a peek ahead ... if i%2: ... # We can get a peek at the next object without disturbing the wrapped generator: ... print "peeking ahead, the next object will be: ", g_with_peek.peek() 0 1 peeking ahead, the next object will be: 2 2 3 peeking ahead, the next object will be: 4 4 """ def __init__(self, generator): """Initialize the generator object. generator: A generator object to be wrapped """ self.generator = generator self.have_peek = False def __iter__(self): return self def next(self): #@ReservedAssignment """Advance to the next object""" if self.have_peek: self.have_peek = False return self.peek_obj else: return self.generator.next() def peek(self): """Take a peek at the next object""" if not self.have_peek: self.peek_obj = self.generator.next() self.have_peek = True return self.peek_obj def tobool(x): """Convert an object to boolean. Examples: >>> print tobool('TRUE') True >>> print tobool(True) True >>> print tobool(1) True >>> print tobool('FALSE') False >>> print tobool(False) False >>> print tobool(0) False >>> print tobool('Foo') Traceback (most recent call last): ValueError: Unknown boolean specifier: 'Foo'. >>> print tobool(None) Traceback (most recent call last): ValueError: Unknown boolean specifier: 'None'. """ try: if x.lower() == 'true': return True elif x.lower() == 'false': return False except AttributeError: pass try: return bool(int(x)) except (ValueError, TypeError): pass raise ValueError("Unknown boolean specifier: '%s'." % x) if __name__ == '__main__': import doctest if not doctest.testmod().failed: print "PASSED"