Tslibs offsets validation

pandas/_libs/tslibs/offsets.pyx

@@ -212,13 +212,66 @@ def _validate_business_time(t_input):
             raise ValueError("time data must match '%H:%M' format")
     elif isinstance(t_input, dt_time):
         if t_input.second != 0 or t_input.microsecond != 0:
-            raise ValueError(
-                "time data must be specified only with hour and minute")
+            raise ValueError("time data must be specified only with "
+                             "hour and minute")
         return t_input
     else:
         raise ValueError("time data must be string or datetime.time")
 
 
+def _validate_n(n):
+    """
+    Require that `n` be a nonzero integer.
+
+    Parameters
+    ----------
+    n : int
+
+    Raises
+    ------
+    ValueError
+    """
+    if n == 0 or not isinstance(n, int):
+        raise ValueError("N cannot be 0")
+
+
+def _validate_month(month):
+    """
+    Require that `month` be an integer between 1 and 12 inclusive.
+
+    Parameters
+    ----------
+    month : int
+
+    Raises
+    ------
+    ValueError
+    """
+    if not isinstance(month, int) or not 1 <= month <= 12:
+        raise ValueError("Month must go from 1 to 12")
+
+
+def _validate_weekday(weekday, allow_none=False):
+    """
+    Require that `weekday` be an integer between 0 and 6, inclusive, or that
+    None be explicitly allowed.
+
+    Parameters
+    ----------
+    weekday : int (or None)
+    allow_none : bool, default False
+
+    Raises
+    ------
+    ValueError
+    """
+    if allow_none and weekday is None:
+        pass
+    elif not isinstance(weekday, int) or not 0 <= weekday <= 6:
+        raise ValueError("weekday must be 0<=weekday<=6, got "
+                         "{day}".format(day=weekday))
+
+
 # ---------------------------------------------------------------------
 # Constructor Helpers
 

pandas/tests/tseries/test_offsets.py

@@ -2192,7 +2192,7 @@ def test_repr(self):
     def test_corner(self):
         pytest.raises(ValueError, Week, weekday=7)
         tm.assert_raises_regex(
-            ValueError, "Day must be", Week, weekday=-1)
+            ValueError, "weekday must be", Week, weekday=-1)
 
     def test_isAnchored(self):
         assert Week(weekday=0).isAnchored()
@@ -2263,9 +2263,9 @@ def test_constructor(self):
                                n=1, week=4, weekday=0)
         tm.assert_raises_regex(ValueError, "^Week", WeekOfMonth,
                                n=1, week=-1, weekday=0)
-        tm.assert_raises_regex(ValueError, "^Day", WeekOfMonth,
+        tm.assert_raises_regex(ValueError, "^weekday", WeekOfMonth,
                                n=1, week=0, weekday=-1)
-        tm.assert_raises_regex(ValueError, "^Day", WeekOfMonth,
+        tm.assert_raises_regex(ValueError, "^weekday", WeekOfMonth,
                                n=1, week=0, weekday=7)
 
     def test_repr(self):
@@ -2347,10 +2347,10 @@ def test_constructor(self):
         tm.assert_raises_regex(ValueError, "^N cannot be 0",
                                LastWeekOfMonth, n=0, weekday=1)
 
-        tm.assert_raises_regex(ValueError, "^Day", LastWeekOfMonth, n=1,
+        tm.assert_raises_regex(ValueError, "^weekday", LastWeekOfMonth, n=1,
                                weekday=-1)
         tm.assert_raises_regex(
-            ValueError, "^Day", LastWeekOfMonth, n=1, weekday=7)
+            ValueError, "^weekday", LastWeekOfMonth, n=1, weekday=7)
 
     def test_offset(self):
         # Saturday

pandas/tseries/offsets.py

@@ -18,7 +18,8 @@
 from pandas._libs.tslibs.offsets import (
     ApplyTypeError,
     as_datetime, _is_normalized,
-    _get_firstbday, _get_calendar, _to_dt64, _validate_business_time,
+    _get_firstbday, _get_calendar, _to_dt64,
+    _validate_business_time, _validate_n, _validate_month, _validate_weekday,
     _int_to_weekday, _weekday_to_int,
     _determine_offset,
     apply_index_wraps,
@@ -1398,10 +1399,7 @@ def __init__(self, n=1, normalize=False, weekday=None):
         self.normalize = normalize
         self.weekday = weekday
 
-        if self.weekday is not None:
-            if self.weekday < 0 or self.weekday > 6:
-                raise ValueError('Day must be 0<=day<=6, got {day}'
-                                 .format(day=self.weekday))
+        _validate_weekday(weekday, allow_none=True)
 
         self.kwds = {'weekday': weekday}
 
@@ -1490,12 +1488,8 @@ def __init__(self, n=1, normalize=False, week=None, weekday=None):
         self.weekday = weekday
         self.week = week
 
-        if self.n == 0:
-            raise ValueError('N cannot be 0')
-
-        if self.weekday < 0 or self.weekday > 6:
-            raise ValueError('Day must be 0<=day<=6, got {day}'
-                             .format(day=self.weekday))
+        _validate_n(n)
+        _validate_weekday(weekday)
         if self.week < 0 or self.week > 3:
             raise ValueError('Week must be 0<=week<=3, got {week}'
                              .format(week=self.week))
@@ -1586,12 +1580,8 @@ def __init__(self, n=1, normalize=False, weekday=None):
         self.normalize = normalize
         self.weekday = weekday
 
-        if self.n == 0:
-            raise ValueError('N cannot be 0')
-
-        if self.weekday < 0 or self.weekday > 6:
-            raise ValueError('Day must be 0<=day<=6, got {day}'
-                             .format(day=self.weekday))
+        _validate_n(n)
+        _validate_weekday(weekday)
 
         self.kwds = {'weekday': weekday}
 
@@ -1848,8 +1838,7 @@ def __init__(self, n=1, normalize=False, month=None):
         month = month if month is not None else self._default_month
         self.month = month
 
-        if self.month < 1 or self.month > 12:
-            raise ValueError('Month must go from 1 to 12')
+        _validate_month(month)
 
         DateOffset.__init__(self, n=n, normalize=normalize, month=month)
 
@@ -2102,8 +2091,7 @@ def __init__(self, n=1, normalize=False, weekday=0, startingMonth=1,
         self.kwds = {'weekday': weekday, 'startingMonth': startingMonth,
                      'variation': variation}
 
-        if self.n == 0:
-            raise ValueError('N cannot be 0')
+        _validate_n(n)
 
         if self.variation not in ["nearest", "last"]:
             raise ValueError('{variation} is not a valid variation'
@@ -2354,8 +2342,7 @@ def __init__(self, n=1, normalize=False, weekday=0, startingMonth=1,
                      'qtr_with_extra_week': qtr_with_extra_week,
                      'variation': variation}
 
-        if self.n == 0:
-            raise ValueError('N cannot be 0')
+        _validate_n(n)
 
     @cache_readonly
     def _offset(self):