DEPR: Remove legacy offsets

Follow-up to #13590.
Remove legacy offset aliases that remained in
`pandas/tseries/frequencies.py`: `_period_alias_dictionary()` and
`_period_alias_dict`.

Author: agraboso <agraboso@gmail.com>

Closes #13868 from agraboso/follow-13590 and squashes the following commits:

25d932d [agraboso] DEPR: Remove legacy offsets

Author: agraboso

doc/source/whatsnew/v0.19.0.txt

@@ -701,7 +701,7 @@ Removal of prior version deprecations/changes
 - ``Series.to_csv`` has dropped the ``nanRep`` parameter in favor of ``na_rep`` (:issue:`13804`)
 - ``Series.xs``, ``DataFrame.xs``, ``Panel.xs``, ``Panel.major_xs``, and ``Panel.minor_xs`` have dropped the ``copy`` parameter (:issue:`13781`)
 - ``str.split`` has dropped the ``return_type`` parameter in favor of ``expand`` (:issue:`13701`)
-- Removal of the legacy time rules (offset aliases), deprecated since 0.17.0 (this has been alias since 0.8.0) (:issue:`13590`)
+- Removal of the legacy time rules (offset aliases), deprecated since 0.17.0 (this has been alias since 0.8.0) (:issue:`13590`, :issue:`13868`)
 
   Previous Behavior:
 

pandas/src/period.pyx

@@ -681,10 +681,7 @@ cdef class _Period(object):
     @classmethod
     def _maybe_convert_freq(cls, object freq):
 
-        if isinstance(freq, compat.string_types):
-            freq = freq.upper()
-            freq = frequencies._period_alias_dict.get(freq, freq)
-        elif isinstance(freq, (int, tuple)):
+        if isinstance(freq, (int, tuple)):
             code, stride = frequencies.get_freq_code(freq)
             freq = frequencies._get_freq_str(code, stride)
 

pandas/tseries/frequencies.py

@@ -620,113 +620,6 @@ def get_standard_freq(freq):
 })
 
 
-def _period_alias_dictionary():
-    """
-    Build freq alias dictionary to support freqs from original c_dates.c file
-    of the scikits.timeseries library.
-    """
-    alias_dict = {}
-
-    M_aliases = ["M", "MTH", "MONTH", "MONTHLY"]
-    B_aliases = ["B", "BUS", "BUSINESS", "BUSINESSLY", "WEEKDAY"]
-    D_aliases = ["D", "DAY", "DLY", "DAILY"]
-    H_aliases = ["H", "HR", "HOUR", "HRLY", "HOURLY"]
-    T_aliases = ["T", "MIN", "MINUTE", "MINUTELY"]
-    S_aliases = ["S", "SEC", "SECOND", "SECONDLY"]
-    L_aliases = ["L", "ms", "MILLISECOND", "MILLISECONDLY"]
-    U_aliases = ["U", "US", "MICROSECOND", "MICROSECONDLY"]
-    N_aliases = ["N", "NS", "NANOSECOND", "NANOSECONDLY"]
-
-    for k in M_aliases:
-        alias_dict[k] = 'M'
-
-    for k in B_aliases:
-        alias_dict[k] = 'B'
-
-    for k in D_aliases:
-        alias_dict[k] = 'D'
-
-    for k in H_aliases:
-        alias_dict[k] = 'H'
-
-    for k in T_aliases:
-        alias_dict[k] = 'T'
-
-    for k in S_aliases:
-        alias_dict[k] = 'S'
-
-    for k in L_aliases:
-        alias_dict[k] = 'L'
-
-    for k in U_aliases:
-        alias_dict[k] = 'U'
-
-    for k in N_aliases:
-        alias_dict[k] = 'N'
-
-    A_prefixes = ["A", "Y", "ANN", "ANNUAL", "ANNUALLY", "YR", "YEAR",
-                  "YEARLY"]
-
-    Q_prefixes = ["Q", "QTR", "QUARTER", "QUARTERLY", "Q-E",
-                  "QTR-E", "QUARTER-E", "QUARTERLY-E"]
-
-    month_names = [
-        ["DEC", "DECEMBER"],
-        ["JAN", "JANUARY"],
-        ["FEB", "FEBRUARY"],
-        ["MAR", "MARCH"],
-        ["APR", "APRIL"],
-        ["MAY", "MAY"],
-        ["JUN", "JUNE"],
-        ["JUL", "JULY"],
-        ["AUG", "AUGUST"],
-        ["SEP", "SEPTEMBER"],
-        ["OCT", "OCTOBER"],
-        ["NOV", "NOVEMBER"]]
-
-    seps = ["@", "-"]
-
-    for k in A_prefixes:
-        alias_dict[k] = 'A'
-        for m_tup in month_names:
-            for sep in seps:
-                m1, m2 = m_tup
-                alias_dict[k + sep + m1] = 'A-' + m1
-                alias_dict[k + sep + m2] = 'A-' + m1
-
-    for k in Q_prefixes:
-        alias_dict[k] = 'Q'
-        for m_tup in month_names:
-            for sep in seps:
-                m1, m2 = m_tup
-                alias_dict[k + sep + m1] = 'Q-' + m1
-                alias_dict[k + sep + m2] = 'Q-' + m1
-
-    W_prefixes = ["W", "WK", "WEEK", "WEEKLY"]
-
-    day_names = [
-        ["SUN", "SUNDAY"],
-        ["MON", "MONDAY"],
-        ["TUE", "TUESDAY"],
-        ["WED", "WEDNESDAY"],
-        ["THU", "THURSDAY"],
-        ["FRI", "FRIDAY"],
-        ["SAT", "SATURDAY"]]
-
-    for k in W_prefixes:
-        alias_dict[k] = 'W'
-        for d_tup in day_names:
-            for sep in ["@", "-"]:
-                d1, d2 = d_tup
-                alias_dict[k + sep + d1] = 'W-' + d1
-                alias_dict[k + sep + d2] = 'W-' + d1
-
-    return alias_dict
-
-
-_period_alias_dict = _period_alias_dictionary()
-
-
 def _period_str_to_code(freqstr):
     freqstr = _lite_rule_alias.get(freqstr, freqstr)
 

pandas/tseries/tests/test_period.py

@@ -457,10 +457,14 @@ def test_period_deprecated_freq(self):
             for freq in freqs:
                 with self.assertRaisesRegexp(ValueError, msg):
                     Period('2016-03-01 09:00', freq=freq)
+                with self.assertRaisesRegexp(ValueError, msg):
+                    Period(ordinal=1, freq=freq)
 
-                # check supported freq-aliases still works
-                p = Period('2016-03-01 09:00', freq=exp)
-                tm.assertIsInstance(p, Period)
+            # check supported freq-aliases still works
+            p1 = Period('2016-03-01 09:00', freq=exp)
+            p2 = Period(ordinal=1, freq=exp)
+            tm.assertIsInstance(p1, Period)
+            tm.assertIsInstance(p2, Period)
 
     def test_hash(self):
         self.assertEqual(hash(Period('2011-01', freq='M')),