BUG: Can't get period code with frequency alias 'minute' or 'Minute'

closes #11854
closes #12540

doc/source/whatsnew/v0.18.1.txt

@@ -88,6 +88,8 @@ Performance Improvements
 Bug Fixes
 ~~~~~~~~~
 
+- Bug in ``Period`` and ``PeriodIndex`` creation raises ``KeyError`` if ``freq="Minute"`` is specified. Note that "Minute" freq is deprecated in v0.17.0, and recommended to use ``freq="T"`` instead (:issue:`11854`)
+
 - Bug in ``value_counts`` when ``normalize=True`` and ``dropna=True`` where nulls still contributed to the normalized count (:issue:`12558`)
 
 - Bug in ``CategoricalIndex.get_loc`` returns different result from regular ``Index`` (:issue:`12531`)

pandas/src/period.pyx

@@ -657,6 +657,7 @@ cdef class Period(object):
 
         if isinstance(freq, compat.string_types):
             from pandas.tseries.frequencies import _period_alias_dict
+            freq = freq.upper()
             freq = _period_alias_dict.get(freq, freq)
         elif isinstance(freq, (int, tuple)):
             from pandas.tseries.frequencies import get_freq_code as _gfc

pandas/tseries/frequencies.py

@@ -385,7 +385,8 @@ def get_period_alias(offset_str):
     'Min': 'T',
     'min': 'T',
     'ms': 'L',
-    'us': 'U'
+    'us': 'U',
+    'ns': 'N'
 }
 
 # TODO: Can this be killed?
@@ -683,7 +684,7 @@ def _period_alias_dictionary():
     alias_dict = {}
 
     M_aliases = ["M", "MTH", "MONTH", "MONTHLY"]
-    B_aliases = ["B", "BUS", "BUSINESS", "BUSINESSLY", 'WEEKDAY']
+    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"]
@@ -705,7 +706,7 @@ def _period_alias_dictionary():
         alias_dict[k] = 'H'
 
     for k in T_aliases:
-        alias_dict[k] = 'Min'
+        alias_dict[k] = 'T'
 
     for k in S_aliases:
         alias_dict[k] = 'S'

pandas/tseries/tests/test_frequencies.py

@@ -170,6 +170,47 @@ def test_get_rule_month():
     assert (result == 'MAY')
 
 
+def test_period_str_to_code():
+    assert (frequencies._period_str_to_code('A') == 1000)
+    assert (frequencies._period_str_to_code('A-DEC') == 1000)
+    assert (frequencies._period_str_to_code('A-JAN') == 1001)
+    assert (frequencies._period_str_to_code('Q') == 2000)
+    assert (frequencies._period_str_to_code('Q-DEC') == 2000)
+    assert (frequencies._period_str_to_code('Q-FEB') == 2002)
+
+    def _assert_depr(freq, expected, aliases):
+        assert isinstance(aliases, list)
+        assert (frequencies._period_str_to_code(freq) == expected)
+
+        for alias in aliases:
+            with tm.assert_produces_warning(FutureWarning,
+                                            check_stacklevel=False):
+                assert (frequencies._period_str_to_code(alias) == expected)
+
+    _assert_depr("M", 3000, ["MTH", "MONTH", "MONTHLY"])
+
+    assert (frequencies._period_str_to_code('W') == 4000)
+    assert (frequencies._period_str_to_code('W-SUN') == 4000)
+    assert (frequencies._period_str_to_code('W-FRI') == 4005)
+
+    _assert_depr("B", 5000, ["BUS", "BUSINESS", "BUSINESSLY", "WEEKDAY"])
+    _assert_depr("D", 6000, ["DAY", "DLY", "DAILY"])
+    _assert_depr("H", 7000, ["HR", "HOUR", "HRLY", "HOURLY"])
+
+    _assert_depr("T", 8000, ["minute", "MINUTE", "MINUTELY"])
+    assert (frequencies._period_str_to_code('Min') == 8000)
+
+    _assert_depr("S", 9000, ["sec", "SEC", "SECOND", "SECONDLY"])
+    _assert_depr("L", 10000, ["MILLISECOND", "MILLISECONDLY"])
+    assert (frequencies._period_str_to_code('ms') == 10000)
+
+    _assert_depr("U", 11000, ["MICROSECOND", "MICROSECONDLY"])
+    assert (frequencies._period_str_to_code('US') == 11000)
+
+    _assert_depr("N", 12000, ["NANOSECOND", "NANOSECONDLY"])
+    assert (frequencies._period_str_to_code('NS') == 12000)
+
+
 class TestFrequencyCode(tm.TestCase):
     def test_freq_code(self):
         self.assertEqual(frequencies.get_freq('A'), 1000)

pandas/tseries/tests/test_period.py

@@ -22,7 +22,7 @@
 import pandas as pd
 import numpy as np
 from numpy.random import randn
-from pandas.compat import range, lrange, lmap, zip, text_type, PY3
+from pandas.compat import range, lrange, lmap, zip, text_type, PY3, iteritems
 from pandas.compat.numpy_compat import np_datetime64_compat
 
 from pandas import (Series, DataFrame,
@@ -36,8 +36,6 @@
 class TestPeriodProperties(tm.TestCase):
     "Test properties such as year, month, weekday, etc...."
 
-    #
-
     def test_quarterly_negative_ordinals(self):
         p = Period(ordinal=-1, freq='Q-DEC')
         self.assertEqual(p.year, 1969)
@@ -440,6 +438,24 @@ def test_freq_str(self):
         self.assertEqual(i1.freq, offsets.Minute())
         self.assertEqual(i1.freqstr, 'T')
 
+    def test_period_deprecated_freq(self):
+        cases = {"M": ["MTH", "MONTH", "MONTHLY", "Mth", "month", "monthly"],
+                 "B": ["BUS", "BUSINESS", "BUSINESSLY", "WEEKDAY", "bus"],
+                 "D": ["DAY", "DLY", "DAILY", "Day", "Dly", "Daily"],
+                 "H": ["HR", "HOUR", "HRLY", "HOURLY", "hr", "Hour", "HRly"],
+                 "T": ["minute", "MINUTE", "MINUTELY", "minutely"],
+                 "S": ["sec", "SEC", "SECOND", "SECONDLY", "second"],
+                 "L": ["MILLISECOND", "MILLISECONDLY", "millisecond"],
+                 "U": ["MICROSECOND", "MICROSECONDLY", "microsecond"],
+                 "N": ["NANOSECOND", "NANOSECONDLY", "nanosecond"]}
+        for exp, freqs in iteritems(cases):
+            for freq in freqs:
+
+                with tm.assert_produces_warning(FutureWarning,
+                                                check_stacklevel=False):
+                    res = pd.Period('2016-03-01 09:00', freq=freq)
+                self.assertEqual(res, Period('2016-03-01 09:00', freq=exp))
+
     def test_repr(self):
         p = Period('Jan-2000')
         self.assertIn('2000-01', repr(p))