Does a day of the week/month fall between two dates?

README

@@ -1,4 +1,7 @@
-A collection of useful scripts that don't fit anywhere else
+A collection of useful scripts and snippets that don't fit anywhere else
+
+falls_between.py: given a day of the week ("tue") or a day of the
+month (15), did it occur between two given dates?
 
 fotogr: Search for strings in files named Keyword beneath the current directory.
 

falls_between.py

@@ -0,0 +1,141 @@
+#! /usr/bin/env python
+
+# Does a day of week or month fall between two dates?
+# Copyright 2012 by Akkana Peck: share and enjoy under the GPLv2 or later.
+
+import time
+
+def falls_between(when, time1, time2) :
+    """Does a given day-of-week or day-of-month fall between
+       the two given times? It is presumed that time1 <= time2.
+       If when == "Tue", did we cross a tuesday getting from time1 to time2?
+       If when == 15, did we cross the 15th of a month?
+       If when == none, return True.
+       If when matches time2, return True.
+    """
+    if not when or type(len) is str and len(when) <= 0 :
+        return True
+
+    # We need both times both in seconds since epoch and in struct_time:
+    def both_time_types(t) :
+        """Given a time that might be either seconds since epoch or struct_time,
+           return a tuple of (seconds, struct_time).
+        """
+        if type(t) is time.struct_time :
+            return time.mktime(t), t
+        elif type(t) is int or type(t) is float :
+            return t, time.localtime(t)
+        else : raise ValueError("%s not int or struct_time" % str(t))
+
+    (t1, st1) = both_time_types(time1)
+    (t2, st2) = both_time_types(time2)
+
+    daysdiff = (t2 - t1) / 60. / 60. / 24.
+
+    # Is it a day of the month?
+    try :
+        day_of_month = int(when)
+
+        # It is a day of the month! How many days in between the two dates?
+        if daysdiff > 31 :
+            return True
+
+        # Now we know the two dates differ by less than a month.
+        # Are time1 and time2 both in the same month? Then it's easy.
+        if st1.tm_mon == st2.tm_mon :
+            return st1.tm_mday <= day_of_month and st2.tm_mday >= day_of_month
+
+        # Else time1 is the month prior to time2, so:
+        return st1.tm_mday < day_of_month or day_of_month <= st2.tm_mday
+
+    except ValueError :  # Not an integer, probably a string.
+        pass
+
+    if type(when) is not str :
+        raise ValueError("%s must be a string or integer" % when)
+
+    # Okay, not a day of the month. Is it a day of the week?
+    # We have to start with Monday because struct_time.tm_wday does.
+    weekdays = [ 'mo', 'tu', 'we', 'th', 'fr', 'sa', 'su' ]
+    if len(when) < 2 :
+        raise ValueError("%s too short: days must have at least 2 chars" % when)
+
+    when = when[0:2].lower()
+    if when not in weekdays :
+        raise ValueError("%s is a string but not a day" % when)
+
+    # Whew -- we know it's a day of the week.
+
+    # Has more than a week passed? Then it encompasses all weekdays.
+    if daysdiff > 7 :
+        return True
+
+    day_of_week = weekdays.index(when)
+    return  (st2.tm_wday - day_of_week) % 7 < daysdiff
+
+# Unit tests:
+if __name__ == "__main__" :
+    #
+    # Day of week tests:
+    #
+    assert falls_between('Mon',
+                         time.strptime('Sun Aug 12 16:00:00 2012'),
+                         time.strptime('Wed Aug 15 16:00:00 2012'))
+    assert falls_between('we',
+                         time.strptime('Sun Aug 12 16:00:00 2012'),
+                         time.strptime('Wed Aug 15 16:00:00 2012'))
+    assert falls_between('monday',
+                         time.strptime('Wed Aug 01 16:00:00 2012'),
+                         time.strptime('Wed Aug 15 16:00:00 2012'))
+    assert falls_between('Mon',
+                         time.strptime('Fri Aug 12 16:00:00 2011'),
+                         time.strptime('Sun Aug 12 16:00:00 2012'))
+    assert not falls_between('Tuesday',
+                             time.strptime('Wed Aug 01 16:00:00 2012'),
+                             time.strptime('Sat Aug 04 16:00:00 2012'))
+    assert not falls_between('fri',
+                             time.strptime('Mon Aug 06 16:00:00 2012'),
+                             time.strptime('Thu Aug 09 16:00:00 2012'))
+
+    #
+    # Day of month tests:
+    #
+    assert falls_between(15,
+                         time.strptime('Sun Aug 12 16:00:00 2012'),
+                         time.strptime('Wed Aug 15 16:00:00 2012'))
+    assert falls_between(13,
+                         time.strptime('Sun Aug 12 16:00:00 2012'),
+                         time.strptime('Wed Aug 15 16:00:00 2012'))
+    assert falls_between(13,
+                         time.strptime('Sun Jul 22 16:00:00 2012'),
+                         time.strptime('Wed Aug 15 16:00:00 2012'))
+    assert falls_between(28,
+                         time.strptime('Sun Jul 22 16:00:00 2012'),
+                         time.strptime('Wed Aug 15 16:00:00 2012'))
+    assert not falls_between(20,
+                         time.strptime('Sun Jul 22 16:00:00 2012'),
+                         time.strptime('Wed Aug 15 16:00:00 2012'))
+    assert not falls_between(17,
+                             time.strptime('Sun Aug 12 16:00:00 2012'),
+                             time.strptime('Wed Aug 15 16:00:00 2012'))
+    assert not falls_between(17,
+                             time.strptime('Tue Aug 07 16:00:00 2012'),
+                             time.strptime('Wed Aug 15 16:00:00 2012'))
+
+    #
+    # Make sure ints and floats both work:
+    #
+    assert falls_between(15,
+                         time.strptime('Sun Aug 12 16:00:00 2012'),
+                         1345074924)
+    assert falls_between(15,
+                         time.strptime('Sun Aug 12 16:00:00 2012'),
+                         1345074924.2)
+    assert not falls_between(17,
+                             time.strptime('Tue Aug 07 16:00:00 2012'),
+                             1345074924)
+    assert not falls_between(17,
+                             time.strptime('Tue Aug 07 16:00:00 2012'),
+                             1345074924.53)
+
+    print "All tests passed!"