Make smart futures avoid polling.

[python_utils.git] / datetime_utils.py

diff --git a/datetime_utils.py b/datetime_utils.py
index c100057d3a306a0efb482418479a3857dcc07b93..7c5516b594b314aed141b4494e7eed5b820770f3 100644 (file)
--- a/datetime_utils.py
+++ b/datetime_utils.py
@@ -16,18 +16,87 @@ import constants
 logger = logging.getLogger(__name__)
 
 
+def is_timezone_aware(dt: datetime.datetime) -> bool:
+    """See: https://docs.python.org/3/library/datetime.html
+                               #determining-if-an-object-is-aware-or-naive
+
+    >>> is_timezone_aware(datetime.datetime.now())
+    False
+
+    >>> is_timezone_aware(now_pacific())
+    True
+
+    """
+    return (
+        dt.tzinfo is not None and
+        dt.tzinfo.utcoffset(dt) is not None
+    )
+
+
+def is_timezone_naive(dt: datetime.datetime) -> bool:
+    return not is_timezone_aware(dt)
+
+
 def replace_timezone(dt: datetime.datetime,
                      tz: datetime.tzinfo) -> datetime.datetime:
     """
-    Replaces the timezone on a datetime object.
+    Replaces the timezone on a datetime object directly (leaving
+    the year, month, day, hour, minute, second, micro, etc... alone).
+    Note: this changes the instant to which this dt refers.
 
     >>> from pytz import UTC
     >>> d = now_pacific()
     >>> d.tzinfo.tzname(d)[0]     # Note: could be PST or PDT
     'P'
+    >>> h = d.hour
     >>> o = replace_timezone(d, UTC)
     >>> o.tzinfo.tzname(o)
     'UTC'
+    >>> o.hour == h
+    True
+
+    """
+    return datetime.datetime(
+        dt.year, dt.month, dt.day, dt.hour, dt.minute, dt.second, dt.microsecond,
+        tzinfo=tz
+    )
+
+
+def replace_time_timezone(t: datetime.time,
+                          tz: datetime.tzinfo) -> datetime.time:
+    """
+    Replaces the timezone on a datetime.time directly without performing
+    any translation.
+
+    >>> t = datetime.time(8, 15, 12, 0, pytz.UTC)
+    >>> t.tzname()
+    'UTC'
+
+    >>> t = replace_time_timezone(t, pytz.timezone('US/Pacific'))
+    >>> t.tzname()
+    'US/Pacific'
+
+    """
+    return t.replace(tzinfo=tz)
+
+
+def translate_timezone(dt: datetime.datetime,
+                       tz: datetime.tzinfo) -> datetime.datetime:
+    """
+    Translates dt into a different timezone by adjusting the year, month,
+    day, hour, minute, second, micro, etc... appropriately.  The returned
+    dt is the same instant in another timezone.
+
+    >>> from pytz import UTC
+    >>> d = now_pacific()
+    >>> d.tzinfo.tzname(d)[0]     # Note: could be PST or PDT
+    'P'
+    >>> h = d.hour
+    >>> o = translate_timezone(d, UTC)
+    >>> o.tzinfo.tzname(o)
+    'UTC'
+    >>> o.hour == h
+    False
 
     """
     return dt.replace(tzinfo=None).astimezone(tz=tz)
@@ -42,9 +111,9 @@ def now() -> datetime.datetime:
 
 def now_pacific() -> datetime.datetime:
     """
-    What time is it?  Result in US/Pacifit time (PST/PDT)
+    What time is it?  Result in US/Pacific time (PST/PDT)
     """
-    return replace_timezone(now(), pytz.timezone("US/Pacific"))
+    return datetime.datetime.now(pytz.timezone("US/Pacific"))
 
 
 def date_to_datetime(date: datetime.date) -> datetime.datetime:
@@ -64,6 +133,42 @@ def date_to_datetime(date: datetime.date) -> datetime.datetime:
     )
 
 
+def time_to_datetime_today(time: datetime.time) -> datetime.datetime:
+    """
+    Given a time, returns that time as a datetime with a date component
+    set based on the current date.  If the time passed is timezone aware,
+    the resulting datetime will also be (and will use the same tzinfo).
+    If the time is timezone naive, the datetime returned will be too.
+
+    >>> t = datetime.time(13, 14, 0)
+    >>> d = now_pacific().date()
+    >>> dt = time_to_datetime_today(t)
+    >>> dt.date() == d
+    True
+
+    >>> dt.time() == t
+    True
+
+    >>> dt.tzinfo == t.tzinfo
+    True
+
+    >>> dt.tzinfo == None
+    True
+
+    >>> t = datetime.time(8, 15, 12, 0, pytz.UTC)
+    >>> t.tzinfo == None
+    False
+
+    >>> dt = time_to_datetime_today(t)
+    >>> dt.tzinfo == None
+    False
+
+    """
+    now = now_pacific()
+    tz = time.tzinfo
+    return datetime.datetime.combine(now, time, tz)
+
+
 def date_and_time_to_datetime(date: datetime.date,
                               time: datetime.time) -> datetime.datetime:
     """