More type annotations.
[python_utils.git] / datetime_utils.py
index 310ffe154d116348fa65e4c707a421c3c6721de0..6f504f6c304b850e830cffab08d0ed8be67fed39 100644 (file)
@@ -27,18 +27,14 @@ def is_timezone_aware(dt: datetime.datetime) -> bool:
     True
 
     """
-    return (
-        dt.tzinfo is not None and
-        dt.tzinfo.utcoffset(dt) is not None
-    )
+    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:
+def replace_timezone(dt: datetime.datetime, tz: datetime.tzinfo) -> datetime.datetime:
     """
     Replaces the timezone on a datetime object directly (leaving
     the year, month, day, hour, minute, second, micro, etc... alone).
@@ -57,13 +53,35 @@ def replace_timezone(dt: datetime.datetime,
 
     """
     return datetime.datetime(
-        dt.year, dt.month, dt.day, dt.hour, dt.minute, dt.second, dt.microsecond,
-        tzinfo=tz
+        dt.year,
+        dt.month,
+        dt.day,
+        dt.hour,
+        dt.minute,
+        dt.second,
+        dt.microsecond,
+        tzinfo=tz,
     )
 
 
-def translate_timezone(dt: datetime.datetime,
-                       tz: datetime.tzinfo) -> datetime.datetime:
+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
@@ -107,16 +125,48 @@ def date_to_datetime(date: datetime.date) -> datetime.datetime:
     datetime.datetime(2021, 12, 25, 0, 0)
 
     """
-    return datetime.datetime(
-        date.year,
-        date.month,
-        date.day,
-        0, 0, 0, 0
-    )
+    return datetime.datetime(date.year, date.month, date.day, 0, 0, 0, 0)
+
+
+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:
+def date_and_time_to_datetime(
+    date: datetime.date, time: datetime.time
+) -> datetime.datetime:
     """
     Given a date and time, merge them and return a datetime.
 
@@ -139,7 +189,7 @@ def date_and_time_to_datetime(date: datetime.date,
 
 
 def datetime_to_date_and_time(
-        dt: datetime.datetime
+    dt: datetime.datetime,
 ) -> Tuple[datetime.date, datetime.time]:
     """Return the component date and time objects of a datetime.
 
@@ -181,6 +231,7 @@ def datetime_to_time(dt: datetime.datetime) -> datetime.time:
 
 class TimeUnit(enum.Enum):
     """An enum to represent units with which we can compute deltas."""
+
     MONDAYS = 0
     TUESDAYS = 1
     WEDNESDAYS = 2
@@ -211,9 +262,7 @@ class TimeUnit(enum.Enum):
 
 
 def n_timeunits_from_base(
-    count: int,
-    unit: TimeUnit,
-    base: datetime.datetime
+    count: int, unit: TimeUnit, base: datetime.datetime
 ) -> datetime.datetime:
     """Return a datetime that is N units before/after a base datetime.
     e.g.  3 Wednesdays from base datetime, 2 weeks from base date, 10
@@ -255,6 +304,17 @@ def n_timeunits_from_base(
     >>> n_timeunits_from_base(50, TimeUnit.SECONDS, base)
     datetime.datetime(2021, 9, 10, 11, 25, 41, tzinfo=datetime.timezone(datetime.timedelta(days=-1, seconds=61200)))
 
+    Next month corner case -- it will try to make Feb 31, 2022 then count
+    backwards.
+    >>> base = string_to_datetime("2022/01/31 11:24:51AM-0700")[0]
+    >>> n_timeunits_from_base(1, TimeUnit.MONTHS, base)
+    datetime.datetime(2022, 2, 28, 11, 24, 51, tzinfo=datetime.timezone(datetime.timedelta(days=-1, seconds=61200)))
+
+    Last month with the same corner case
+    >>> base = string_to_datetime("2022/03/31 11:24:51AM-0700")[0]
+    >>> n_timeunits_from_base(-1, TimeUnit.MONTHS, base)
+    datetime.datetime(2022, 2, 28, 11, 24, 51, tzinfo=datetime.timezone(datetime.timedelta(days=-1, seconds=61200)))
+
     """
     assert TimeUnit.is_valid(unit)
     if count == 0:
@@ -294,10 +354,8 @@ def n_timeunits_from_base(
             if base.year != old_year:
                 skips = holidays.US(years=base.year).keys()
             if (
-                    base.weekday() < 5 and
-                    datetime.date(base.year,
-                                  base.month,
-                                  base.day) not in skips
+                base.weekday() < 5
+                and datetime.date(base.year, base.month, base.day) not in skips
             ):
                 count -= 1
         return base
@@ -317,16 +375,23 @@ def n_timeunits_from_base(
             new_month %= 12
             year_term += 1
         new_year = base.year + year_term
-        return datetime.datetime(
-            new_year,
-            new_month,
-            base.day,
-            base.hour,
-            base.minute,
-            base.second,
-            base.microsecond,
-            base.tzinfo,
-        )
+        day = base.day
+        while True:
+            try:
+                ret = datetime.datetime(
+                    new_year,
+                    new_month,
+                    day,
+                    base.hour,
+                    base.minute,
+                    base.second,
+                    base.microsecond,
+                    base.tzinfo,
+                )
+                break
+            except ValueError:
+                day -= 1
+        return ret
 
     # N years from base
     elif unit == TimeUnit.YEARS:
@@ -342,13 +407,17 @@ def n_timeunits_from_base(
             base.tzinfo,
         )
 
-    if unit not in set([TimeUnit.MONDAYS,
-                        TimeUnit.TUESDAYS,
-                        TimeUnit.WEDNESDAYS,
-                        TimeUnit.THURSDAYS,
-                        TimeUnit.FRIDAYS,
-                        TimeUnit.SATURDAYS,
-                        TimeUnit.SUNDAYS]):
+    if unit not in set(
+        [
+            TimeUnit.MONDAYS,
+            TimeUnit.TUESDAYS,
+            TimeUnit.WEDNESDAYS,
+            TimeUnit.THURSDAYS,
+            TimeUnit.FRIDAYS,
+            TimeUnit.SATURDAYS,
+            TimeUnit.SUNDAYS,
+        ]
+    ):
         raise ValueError(unit)
 
     # N weekdays from base (e.g. 4 wednesdays from today)
@@ -366,14 +435,14 @@ def n_timeunits_from_base(
 
 
 def get_format_string(
-        *,
-        date_time_separator=" ",
-        include_timezone=True,
-        include_dayname=False,
-        use_month_abbrevs=False,
-        include_seconds=True,
-        include_fractional=False,
-        twelve_hour=True,
+    *,
+    date_time_separator=" ",
+    include_timezone=True,
+    include_dayname=False,
+    use_month_abbrevs=False,
+    include_seconds=True,
+    include_fractional=False,
+    twelve_hour=True,
 ) -> str:
     """
     Helper to return a format string without looking up the documentation
@@ -448,20 +517,21 @@ def datetime_to_string(
         include_dayname=include_dayname,
         include_seconds=include_seconds,
         include_fractional=include_fractional,
-        twelve_hour=twelve_hour)
+        twelve_hour=twelve_hour,
+    )
     return dt.strftime(fstring).strip()
 
 
 def string_to_datetime(
-        txt: str,
-        *,
-        date_time_separator=" ",
-        include_timezone=True,
-        include_dayname=False,
-        use_month_abbrevs=False,
-        include_seconds=True,
-        include_fractional=False,
-        twelve_hour=True,
+    txt: str,
+    *,
+    date_time_separator=" ",
+    include_timezone=True,
+    include_dayname=False,
+    use_month_abbrevs=False,
+    include_seconds=True,
+    include_fractional=False,
+    twelve_hour=True,
 ) -> Tuple[datetime.datetime, str]:
     """A nice way to convert a string into a datetime.  Returns both the
     datetime and the format string used to parse it.  Also consider
@@ -480,11 +550,9 @@ def string_to_datetime(
         include_dayname=include_dayname,
         include_seconds=include_seconds,
         include_fractional=include_fractional,
-        twelve_hour=twelve_hour)
-    return (
-        datetime.datetime.strptime(txt, fstring),
-        fstring
+        twelve_hour=twelve_hour,
     )
+    return (datetime.datetime.strptime(txt, fstring), fstring)
 
 
 def timestamp() -> str:
@@ -651,7 +719,7 @@ def parse_duration(duration: str) -> int:
     return seconds
 
 
-def describe_duration(seconds: int, *, include_seconds = False) -> str:
+def describe_duration(seconds: int, *, include_seconds=False) -> str:
     """
     Describe a duration represented as a count of seconds nicely.
 
@@ -712,7 +780,7 @@ def describe_timedelta(delta: datetime.timedelta) -> str:
     '1 day, and 10 minutes'
 
     """
-    return describe_duration(delta.total_seconds())
+    return describe_duration(int(delta.total_seconds()))  # Note: drops milliseconds
 
 
 def describe_duration_briefly(seconds: int, *, include_seconds=False) -> str:
@@ -757,9 +825,12 @@ def describe_timedelta_briefly(delta: datetime.timedelta) -> str:
     '1d 10m'
 
     """
-    return describe_duration_briefly(delta.total_seconds())
+    return describe_duration_briefly(
+        int(delta.total_seconds())
+    )  # Note: drops milliseconds
 
 
 if __name__ == '__main__':
     import doctest
+
     doctest.testmod()