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CLN/ENH: Stop instantiating all offsets on load. #5189

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Oct 15, 2013
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CLN/ENH: Stop instantiating all offsets on load. #5189

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4 changes: 4 additions & 0 deletions doc/source/release.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -394,6 +394,10 @@ See :ref:`Internal Refactoring<whatsnew_0130.refactoring>`
bs4/lxml (:issue:`4770`).
- Removed the ``keep_internal`` keyword parameter in
``pandas/core/groupby.py`` because it wasn't being used (:issue:`5102`).
- Base ``DateOffsets`` are no longer all instantiated on importing pandas,
instead they are generated and cached on the fly. The internal
representation and handling of DateOffsets has also been clarified.
(:issue:`5189`, related :issue:`5004`)

.. _release.bug_fixes-0.13.0:

Expand Down
207 changes: 28 additions & 179 deletions pandas/tseries/frequencies.py
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,6 @@
import pandas.core.common as com
import pandas.lib as lib
import pandas.tslib as tslib
from pandas import _np_version_under1p7


class FreqGroup(object):
Expand Down Expand Up @@ -125,162 +124,15 @@ def _get_freq_str(base, mult=1):
MonthEnd, BMonthBegin, BMonthEnd,
QuarterBegin, QuarterEnd, BQuarterBegin,
BQuarterEnd, YearBegin, YearEnd,
BYearBegin, BYearEnd,
BYearBegin, BYearEnd, _make_offset
)
try:
cday = CDay()
except NotImplementedError:
cday = None

_offset_map = {
'D': Day(),
'C': cday,
'B': BDay(),
'H': Hour(),
'T': Minute(),
'S': Second(),
'L': Milli(),
'U': Micro(),
None: None,

# Monthly - Calendar
'M': MonthEnd(),
'MS': MonthBegin(),

# Monthly - Business
'BM': BMonthEnd(),
'BMS': BMonthBegin(),

# Annual - Calendar
'A-JAN': YearEnd(month=1),
'A-FEB': YearEnd(month=2),
'A-MAR': YearEnd(month=3),
'A-APR': YearEnd(month=4),
'A-MAY': YearEnd(month=5),
'A-JUN': YearEnd(month=6),
'A-JUL': YearEnd(month=7),
'A-AUG': YearEnd(month=8),
'A-SEP': YearEnd(month=9),
'A-OCT': YearEnd(month=10),
'A-NOV': YearEnd(month=11),
'A-DEC': YearEnd(month=12),

# Annual - Calendar (start)
'AS-JAN': YearBegin(month=1),
'AS-FEB': YearBegin(month=2),
'AS-MAR': YearBegin(month=3),
'AS-APR': YearBegin(month=4),
'AS-MAY': YearBegin(month=5),
'AS-JUN': YearBegin(month=6),
'AS-JUL': YearBegin(month=7),
'AS-AUG': YearBegin(month=8),
'AS-SEP': YearBegin(month=9),
'AS-OCT': YearBegin(month=10),
'AS-NOV': YearBegin(month=11),
'AS-DEC': YearBegin(month=12),

# Annual - Business
'BA-JAN': BYearEnd(month=1),
'BA-FEB': BYearEnd(month=2),
'BA-MAR': BYearEnd(month=3),
'BA-APR': BYearEnd(month=4),
'BA-MAY': BYearEnd(month=5),
'BA-JUN': BYearEnd(month=6),
'BA-JUL': BYearEnd(month=7),
'BA-AUG': BYearEnd(month=8),
'BA-SEP': BYearEnd(month=9),
'BA-OCT': BYearEnd(month=10),
'BA-NOV': BYearEnd(month=11),
'BA-DEC': BYearEnd(month=12),

# Annual - Business (Start)
'BAS-JAN': BYearBegin(month=1),
'BAS-FEB': BYearBegin(month=2),
'BAS-MAR': BYearBegin(month=3),
'BAS-APR': BYearBegin(month=4),
'BAS-MAY': BYearBegin(month=5),
'BAS-JUN': BYearBegin(month=6),
'BAS-JUL': BYearBegin(month=7),
'BAS-AUG': BYearBegin(month=8),
'BAS-SEP': BYearBegin(month=9),
'BAS-OCT': BYearBegin(month=10),
'BAS-NOV': BYearBegin(month=11),
'BAS-DEC': BYearBegin(month=12),

# Quarterly - Calendar
# 'Q' : QuarterEnd(startingMonth=3),
'Q-JAN': QuarterEnd(startingMonth=1),
'Q-FEB': QuarterEnd(startingMonth=2),
'Q-MAR': QuarterEnd(startingMonth=3),
'Q-APR': QuarterEnd(startingMonth=4),
'Q-MAY': QuarterEnd(startingMonth=5),
'Q-JUN': QuarterEnd(startingMonth=6),
'Q-JUL': QuarterEnd(startingMonth=7),
'Q-AUG': QuarterEnd(startingMonth=8),
'Q-SEP': QuarterEnd(startingMonth=9),
'Q-OCT': QuarterEnd(startingMonth=10),
'Q-NOV': QuarterEnd(startingMonth=11),
'Q-DEC': QuarterEnd(startingMonth=12),

# Quarterly - Calendar (Start)
'QS': QuarterBegin(startingMonth=1),
'QS-JAN': QuarterBegin(startingMonth=1),
'QS-FEB': QuarterBegin(startingMonth=2),
'QS-MAR': QuarterBegin(startingMonth=3),
'QS-APR': QuarterBegin(startingMonth=4),
'QS-MAY': QuarterBegin(startingMonth=5),
'QS-JUN': QuarterBegin(startingMonth=6),
'QS-JUL': QuarterBegin(startingMonth=7),
'QS-AUG': QuarterBegin(startingMonth=8),
'QS-SEP': QuarterBegin(startingMonth=9),
'QS-OCT': QuarterBegin(startingMonth=10),
'QS-NOV': QuarterBegin(startingMonth=11),
'QS-DEC': QuarterBegin(startingMonth=12),

# Quarterly - Business
'BQ-JAN': BQuarterEnd(startingMonth=1),
'BQ-FEB': BQuarterEnd(startingMonth=2),
'BQ-MAR': BQuarterEnd(startingMonth=3),

'BQ': BQuarterEnd(startingMonth=12),
'BQ-APR': BQuarterEnd(startingMonth=4),
'BQ-MAY': BQuarterEnd(startingMonth=5),
'BQ-JUN': BQuarterEnd(startingMonth=6),
'BQ-JUL': BQuarterEnd(startingMonth=7),
'BQ-AUG': BQuarterEnd(startingMonth=8),
'BQ-SEP': BQuarterEnd(startingMonth=9),
'BQ-OCT': BQuarterEnd(startingMonth=10),
'BQ-NOV': BQuarterEnd(startingMonth=11),
'BQ-DEC': BQuarterEnd(startingMonth=12),

# Quarterly - Business (Start)
'BQS-JAN': BQuarterBegin(startingMonth=1),
'BQS': BQuarterBegin(startingMonth=1),
'BQS-FEB': BQuarterBegin(startingMonth=2),
'BQS-MAR': BQuarterBegin(startingMonth=3),
'BQS-APR': BQuarterBegin(startingMonth=4),
'BQS-MAY': BQuarterBegin(startingMonth=5),
'BQS-JUN': BQuarterBegin(startingMonth=6),
'BQS-JUL': BQuarterBegin(startingMonth=7),
'BQS-AUG': BQuarterBegin(startingMonth=8),
'BQS-SEP': BQuarterBegin(startingMonth=9),
'BQS-OCT': BQuarterBegin(startingMonth=10),
'BQS-NOV': BQuarterBegin(startingMonth=11),
'BQS-DEC': BQuarterBegin(startingMonth=12),

# Weekly
'W-MON': Week(weekday=0),
'W-TUE': Week(weekday=1),
'W-WED': Week(weekday=2),
'W-THU': Week(weekday=3),
'W-FRI': Week(weekday=4),
'W-SAT': Week(weekday=5),
'W-SUN': Week(weekday=6),

}

if not _np_version_under1p7:
_offset_map['N'] = Nano()
#: cache of previously seen offsets
_offset_map = {}

_offset_to_period_map = {
'WEEKDAY': 'D',
Expand Down Expand Up @@ -386,15 +238,6 @@ def get_period_alias(offset_str):
_legacy_reverse_map = dict((v, k) for k, v in
reversed(sorted(compat.iteritems(_rule_aliases))))

# for helping out with pretty-printing and name-lookups

_offset_names = {}
for name, offset in compat.iteritems(_offset_map):
if offset is None:
continue
offset.name = name
_offset_names[offset] = name


def inferTimeRule(index):
from pandas.tseries.index import DatetimeIndex
Expand Down Expand Up @@ -513,22 +356,21 @@ def get_offset(name):
else:
if name in _rule_aliases:
name = _rule_aliases[name]

offset = _offset_map.get(name)

if offset is not None:
return offset
else:
raise ValueError('Bad rule name requested: %s.' % name)
try:
if name not in _offset_map:
# generate and cache offset
offset = _make_offset(name)
_offset_map[name] = offset
return _offset_map[name]
except (ValueError, TypeError, KeyError):
# bad prefix or suffix
pass
raise ValueError('Bad rule name requested: %s.' % name)


getOffset = get_offset


def hasOffsetName(offset):
return offset in _offset_names


def get_offset_name(offset):
"""
Return rule name associated with a DateOffset object
Expand All @@ -537,19 +379,26 @@ def get_offset_name(offset):
--------
get_offset_name(BMonthEnd(1)) --> 'EOM'
"""
name = _offset_names.get(offset)

if name is not None:
return name
else:
if offset is None:
raise ValueError("Offset can't be none!")
# Hack because this is what it did before...
if isinstance(offset, BDay):
if offset.n != 1:
raise ValueError('Bad rule given: %s.' % 'BusinessDays')
else:
return offset.rule_code
try:
return offset.freqstr
except AttributeError:
# Bad offset, give useful error.
raise ValueError('Bad rule given: %s.' % offset)


def get_legacy_offset_name(offset):
"""
Return the pre pandas 0.8.0 name for the date offset
"""
name = _offset_names.get(offset)
name = offset.name
return _legacy_reverse_map.get(name, name)

get_offset_name = get_offset_name
Expand Down Expand Up @@ -652,7 +501,7 @@ def _period_alias_dictionary():
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'

Expand All @@ -679,7 +528,7 @@ def _period_alias_dictionary():

for k in N_aliases:
alias_dict[k] = 'N'

A_prefixes = ["A", "Y", "ANN", "ANNUAL", "ANNUALLY", "YR", "YEAR",
"YEARLY"]

Expand Down
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