ENH: Create a 'Y' alias for date_range yearly frequency

Closes pandas-devgh-9313

Author: imih

pandas/tests/tseries/test_frequencies.py

@@ -248,9 +248,10 @@ def test_anchored_shortcuts(self):
 
  # ensure invalid cases fail as expected
  invalid_anchors = ['SM-0', 'SM-28', 'SM-29',
- 'SM-FOO', 'BSM', 'SM--1'
+ 'SM-FOO', 'BSM', 'SM--1',
  'SMS-1', 'SMS-28', 'SMS-30',
- 'SMS-BAR', 'BSMS', 'SMS--2']
+ 'SMS-BAR', 'SMS-BYR' 'BSMS',
+ 'SMS--2']
  for invalid_anchor in invalid_anchors:
  with tm.assert_raises_regex(ValueError,
  'Invalid frequency: '):
@@ -292,11 +293,15 @@ def test_get_rule_month():
 
  result = frequencies._get_rule_month('A-DEC')
  assert (result == 'DEC')
+ result = frequencies._get_rule_month('Y-DEC')
+ assert (result == 'DEC')
  result = frequencies._get_rule_month(offsets.YearEnd())
  assert (result == 'DEC')
 
  result = frequencies._get_rule_month('A-MAY')
  assert (result == 'MAY')
+ result = frequencies._get_rule_month('Y-MAY')
+ assert (result == 'MAY')
  result = frequencies._get_rule_month(offsets.YearEnd(month=5))
  assert (result == 'MAY')
 
@@ -305,6 +310,10 @@ 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('Y') == 1000)
+ assert (frequencies._period_str_to_code('Y-DEC') == 1000)
+ assert (frequencies._period_str_to_code('Y-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)
@@ -349,6 +358,10 @@ def test_freq_code(self):
  assert frequencies.get_freq('3A') == 1000
  assert frequencies.get_freq('-1A') == 1000
 
+ assert frequencies.get_freq('Y') == 1000
+ assert frequencies.get_freq('3Y') == 1000
+ assert frequencies.get_freq('-1Y') == 1000
+
  assert frequencies.get_freq('W') == 4000
  assert frequencies.get_freq('W-MON') == 4001
  assert frequencies.get_freq('W-FRI') == 4005
@@ -369,6 +382,13 @@ def test_freq_group(self):
  assert frequencies.get_freq_group('-1A') == 1000
  assert frequencies.get_freq_group('A-JAN') == 1000
  assert frequencies.get_freq_group('A-MAY') == 1000
+
+ assert frequencies.get_freq_group('Y') == 1000
+ assert frequencies.get_freq_group('3Y') == 1000
+ assert frequencies.get_freq_group('-1Y') == 1000
+ assert frequencies.get_freq_group('Y-JAN') == 1000
+ assert frequencies.get_freq_group('Y-MAY') == 1000
+
  assert frequencies.get_freq_group(offsets.YearEnd()) == 1000
  assert frequencies.get_freq_group(offsets.YearEnd(month=1)) == 1000
  assert frequencies.get_freq_group(offsets.YearEnd(month=5)) == 1000
@@ -790,12 +810,6 @@ def test_series(self):
  for freq in [None, 'L']:
  s = Series(period_range('2013', periods=10, freq=freq))
  pytest.raises(TypeError, lambda: frequencies.infer_freq(s))
- for freq in ['Y']:
-
- msg = frequencies._INVALID_FREQ_ERROR
- with tm.assert_raises_regex(ValueError, msg):
- s = Series(period_range('2013', periods=10, freq=freq))
- pytest.raises(TypeError, lambda: frequencies.infer_freq(s))
 
  # DateTimeIndex
  for freq in ['M', 'L', 'S']:
@@ -812,11 +826,12 @@ def test_legacy_offset_warnings(self):
  'W@FRI', 'W@SAT', 'W@SUN', 'Q@JAN', 'Q@FEB', 'Q@MAR',
  'A@JAN', 'A@FEB', 'A@MAR', 'A@APR', 'A@MAY', 'A@JUN',
  'A@JUL', 'A@AUG', 'A@SEP', 'A@OCT', 'A@NOV', 'A@DEC',
- 'WOM@1MON', 'WOM@2MON', 'WOM@3MON', 'WOM@4MON',
- 'WOM@1TUE', 'WOM@2TUE', 'WOM@3TUE', 'WOM@4TUE',
- 'WOM@1WED', 'WOM@2WED', 'WOM@3WED', 'WOM@4WED',
- 'WOM@1THU', 'WOM@2THU', 'WOM@3THU', 'WOM@4THU'
- 'WOM@1FRI', 'WOM@2FRI', 'WOM@3FRI', 'WOM@4FRI']
+ 'Y@JAN', 'WOM@1MON', 'WOM@2MON', 'WOM@3MON',
+ 'WOM@4MON', 'WOM@1TUE', 'WOM@2TUE', 'WOM@3TUE',
+ 'WOM@4TUE', 'WOM@1WED', 'WOM@2WED', 'WOM@3WED',
+ 'WOM@4WED', 'WOM@1THU', 'WOM@2THU', 'WOM@3THU',
+ 'WOM@4THU', 'WOM@1FRI', 'WOM@2FRI', 'WOM@3FRI',
+ 'WOM@4FRI']
 
  msg = frequencies._INVALID_FREQ_ERROR
  for freq in freqs:

pandas/tseries/frequencies.py

@@ -422,6 +422,27 @@ def get_period_alias(offset_str):
  return _offset_to_period_map.get(offset_str, None)
 
 
+_pure_alias = {
+ # 'A' is equivalent to 'Y'.
+ 'Y': 'A',
+ 'YS': 'AS',
+ 'BY': 'BA',
+ 'BYS': 'BAS',
+ 'Y-DEC': 'A-DEC',
+ 'Y-JAN': 'A-JAN',
+ 'Y-FEB': 'A-FEB',
+ 'Y-MAR': 'A-MAR',
+ 'Y-APR': 'A-APR',
+ 'Y-MAY': 'A-MAY',
+ 'Y-JUN': 'A-JUN',
+ 'Y-JUL': 'A-JUL',
+ 'Y-AUG': 'A-AUG',
+ 'Y-SEP': 'A-SEP',
+ 'Y-OCT': 'A-OCT',
+ 'Y-NOV': 'A-NOV',
+}
+
+
 _lite_rule_alias = {
  'W': 'W-SUN',
  'Q': 'Q-DEC',
@@ -718,6 +739,7 @@ def get_standard_freq(freq):
 
 
 def _period_str_to_code(freqstr):
+ freqstr = _pure_alias.get(freqstr, freqstr)
  freqstr = _lite_rule_alias.get(freqstr, freqstr)
 
  if freqstr not in _dont_uppercase: