Add month names

Fix localiztion of months

Add series test and whatsnew notes

Modify test and lint

Add Timestamp rst

Address comments

Lint, move whatsnew, remove hardcoded Monday, check that get_locale is None

create functions instead of attributes

Fix white space

Modify tests

Lint

Rebase and add depreciation message

Deprecate weekday_name, create localizing function in ccalendar.pyx

clean up imports

Address user comments

Try to address ci issues

Author: mroeschke

doc/source/api.rst

@@ -582,6 +582,8 @@ These can be accessed like ``Series.dt.<property>``.
    Series.dt.round
    Series.dt.floor
    Series.dt.ceil
+   Series.dt.month_name
+   Series.dt.day_name
 
 **Timedelta Properties**
 
@@ -1760,6 +1762,8 @@ Time-specific operations
    DatetimeIndex.round
    DatetimeIndex.floor
    DatetimeIndex.ceil
+   DatetimeIndex.month_name
+   DatetimeIndex.day_name
 
 Conversion
 ~~~~~~~~~~
@@ -1955,6 +1959,7 @@ Methods
     Timestamp.combine
     Timestamp.ctime
     Timestamp.date
+    Timestamp.day_name
     Timestamp.dst
     Timestamp.floor
     Timestamp.freq
@@ -1964,6 +1969,7 @@ Methods
     Timestamp.isocalendar
     Timestamp.isoformat
     Timestamp.isoweekday
+    Timestamp.month_name
     Timestamp.normalize
     Timestamp.now
     Timestamp.replace

doc/source/whatsnew/v0.23.0.txt

@@ -306,7 +306,8 @@ Other Enhancements
 - Added :func:`SeriesGroupBy.is_monotonic_increasing` and :func:`SeriesGroupBy.is_monotonic_decreasing` (:issue:`17015`)
 - For subclassed ``DataFrames``, :func:`DataFrame.apply` will now preserve the ``Series`` subclass (if defined) when passing the data to the applied function (:issue:`19822`)
 - :func:`DataFrame.from_dict` now accepts a ``columns`` argument that can be used to specify the column names when ``orient='index'`` is used (:issue:`18529`)
-
+- :meth:`Timestamp.month_name`, :meth:`DatetimeIndex.month_name`, and :meth:`Series.dt.month_name` are now available (:issue:`12805`)
+- :meth:`Timestamp.day_name` and :meth:`DatetimeIndex.day_name` are now available to return day names with a specified locale (:issue:`12806`)
 
 .. _whatsnew_0230.api_breaking:
 
@@ -641,6 +642,7 @@ Deprecations
 - The ``broadcast`` parameter of ``.apply()`` is deprecated in favor of ``result_type='broadcast'`` (:issue:`18577`)
 - The ``reduce`` parameter of ``.apply()`` is deprecated in favor of ``result_type='reduce'`` (:issue:`18577`)
 - The ``order`` parameter of :func:`factorize` is deprecated and will be removed in a future release (:issue:`19727`)
+- :attr:`Timestamp.weekday_name`, :attr:`DatetimeIndex.weekday_name`, and :attr:`Series.dt.weekday_name` are deprecated in favor of :meth:`Timestamp.day_name`, :meth:`DatetimeIndex.day_name`, and :meth:`Series.dt.day_name` (:issue:`12806`)
 
 .. _whatsnew_0230.prior_deprecations:
 

pandas/_libs/tslibs/ccalendar.pyx

@@ -35,11 +35,18 @@ cdef int32_t* _month_offset = [
 # Canonical location for other modules to find name constants
 MONTHS = ['JAN', 'FEB', 'MAR', 'APR', 'MAY', 'JUN', 'JUL',
           'AUG', 'SEP', 'OCT', 'NOV', 'DEC']
+# The first blank line is consistent with calendar.month_name in the calendar
+# standard library
+MONTHS_FULL = ['', 'January', 'February', 'March', 'April', 'May', 'June',
+               'July', 'August', 'September', 'October', 'November',
+               'December']
 MONTH_NUMBERS = {name: num for num, name in enumerate(MONTHS)}
 MONTH_ALIASES = {(num + 1): name for num, name in enumerate(MONTHS)}
 MONTH_TO_CAL_NUM = {name: num + 1 for num, name in enumerate(MONTHS)}
 
 DAYS = ['MON', 'TUE', 'WED', 'THU', 'FRI', 'SAT', 'SUN']
+DAYS_FULL = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday',
+             'Saturday', 'Sunday']
 int_to_weekday = {num: name for num, name in enumerate(DAYS)}
 weekday_to_int = {int_to_weekday[key]: key for key in int_to_weekday}
 
@@ -199,3 +206,28 @@ cpdef int32_t get_day_of_year(int year, int month, int day) nogil:
 
     day_of_year = mo_off + day
     return day_of_year
+
+
+cpdef get_locale_names(object name_type, object time_locale=None):
+    """Returns an array of localized day or month names
+
+    Parameters
+    ----------
+    name_type : string, attribute of LocaleTime() in which to return localized
+        names
+    locale : string
+
+    Returns
+    -------
+    names : list
+
+    """
+    cdef:
+        list locale_names
+
+    import locale
+    from pandas.util.testing import set_locale
+    from strptime import LocaleTime
+    with set_locale(time_locale, locale.LC_TIME):
+        locale_names = getattr(LocaleTime(), name_type)
+    return locale_names

pandas/_libs/tslibs/fields.pyx

@@ -13,7 +13,7 @@ cimport numpy as cnp
 from numpy cimport ndarray, int64_t, int32_t, int8_t
 cnp.import_array()
 
-
+from ccalendar import get_locale_names, MONTHS_FULL, DAYS_FULL
 from ccalendar cimport (get_days_in_month, is_leapyear, dayofweek,
                         get_week_of_year, get_day_of_year)
 from np_datetime cimport (pandas_datetimestruct, pandas_timedeltastruct,
@@ -85,7 +85,8 @@ def build_field_sarray(ndarray[int64_t] dtindex):
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def get_date_name_field(ndarray[int64_t] dtindex, object field):
+def get_date_name_field(ndarray[int64_t] dtindex, object field,
+                        object time_locale=None):
     """
     Given a int64-based datetime index, return array of strings of date
     name based on requested field (e.g. weekday_name)
@@ -96,15 +97,11 @@ def get_date_name_field(ndarray[int64_t] dtindex, object field):
         pandas_datetimestruct dts
         int dow
 
-    _dayname = np.array(
-        ['Monday', 'Tuesday', 'Wednesday', 'Thursday',
-            'Friday', 'Saturday', 'Sunday'],
-        dtype=np.object_)
-
     count = len(dtindex)
     out = np.empty(count, dtype=object)
 
     if field == 'weekday_name':
+        _dayname = np.array(DAYS_FULL, dtype=np.object_)
         for i in range(count):
             if dtindex[i] == NPY_NAT:
                 out[i] = np.nan
@@ -114,6 +111,35 @@ def get_date_name_field(ndarray[int64_t] dtindex, object field):
             dow = dayofweek(dts.year, dts.month, dts.day)
             out[i] = _dayname[dow]
         return out
+    elif field == 'day_name':
+        if time_locale is None:
+            _dayname = np.array(DAYS_FULL, dtype=np.object_)
+        else:
+            _dayname = np.array(get_locale_names('f_weekday', time_locale),
+                                dtype=np.object_)
+        for i in range(count):
+            if dtindex[i] == NPY_NAT:
+                out[i] = np.nan
+                continue
+
+            dt64_to_dtstruct(dtindex[i], &dts)
+            dow = dayofweek(dts.year, dts.month, dts.day)
+            out[i] = _dayname[dow].capitalize()
+        return out
+    elif field == 'month_name':
+        if time_locale is None:
+            _monthname = np.array(MONTHS_FULL, dtype=np.object_)
+        else:
+            _monthname = np.array(get_locale_names('f_month', time_locale),
+                                  dtype=np.object_)
+        for i in range(count):
+            if dtindex[i] == NPY_NAT:
+                out[i] = np.nan
+                continue
+
+            dt64_to_dtstruct(dtindex[i], &dts)
+            out[i] = _monthname[dts.month].capitalize()
+        return out
 
     raise ValueError("Field %s not supported" % field)
 

pandas/_libs/tslibs/nattype.pyx

@@ -1,6 +1,5 @@
 # -*- coding: utf-8 -*-
 # cython: profile=False
-import warnings
 
 from cpython cimport (
     PyFloat_Check, PyComplex_Check,
@@ -39,24 +38,19 @@ _nat_scalar_rules[Py_GE] = False
 # ----------------------------------------------------------------------
 
 
-def _make_nan_func(func_name, cls):
+def _make_nan_func(func_name, doc):
     def f(*args, **kwargs):
         return np.nan
     f.__name__ = func_name
-    f.__doc__ = getattr(cls, func_name).__doc__
+    f.__doc__ = doc
     return f
 
 
-def _make_nat_func(func_name, cls):
+def _make_nat_func(func_name, doc):
     def f(*args, **kwargs):
         return NaT
-
     f.__name__ = func_name
-    if isinstance(cls, str):
-        # passed the literal docstring directly
-        f.__doc__ = cls
-    else:
-        f.__doc__ = getattr(cls, func_name).__doc__
+    f.__doc__ = doc
     return f
 
 
@@ -318,11 +312,36 @@ class NaTType(_NaT):
     # These are the ones that can get their docstrings from datetime.
 
     # nan methods
-    weekday = _make_nan_func('weekday', datetime)
-    isoweekday = _make_nan_func('isoweekday', datetime)
+    weekday = _make_nan_func('weekday', datetime.weekday.__doc__)
+    isoweekday = _make_nan_func('isoweekday', datetime.isoweekday.__doc__)
+    month_name = _make_nan_func('month_name',  # noqa:E128
+        """
+        Return the month name of the Timestamp with specified locale.
+
+        Parameters
+        ----------
+        time_locale : string, default None (English locale)
+            locale determining the language in which to return the month name
+
+        Returns
+        -------
+        month_name : string
+        """)
+    day_name = _make_nan_func('day_name', # noqa:E128
+        """
+        Return the day name of the Timestamp with specified locale.
+
+        Parameters
+        ----------
+        time_locale : string, default None (English locale)
+            locale determining the language in which to return the day name
 
+        Returns
+        -------
+        day_name : string
+        """)
     # _nat_methods
-    date = _make_nat_func('date', datetime)
+    date = _make_nat_func('date', datetime.date.__doc__)
 
     utctimetuple = _make_error_func('utctimetuple', datetime)
     timetz = _make_error_func('timetz', datetime)

pandas/_libs/tslibs/timestamps.pyx

@@ -21,6 +21,7 @@ from util cimport (is_datetime64_object, is_timedelta64_object,
                    INT64_MAX)
 
 cimport ccalendar
+from ccalendar import get_locale_names, MONTHS_FULL, DAYS_FULL
 from conversion import tz_localize_to_utc, date_normalize
 from conversion cimport (tz_convert_single, _TSObject,
                          convert_to_tsobject, convert_datetime_to_tsobject)
@@ -701,8 +702,55 @@ class Timestamp(_Timestamp):
     def dayofweek(self):
         return self.weekday()
 
+    def day_name(self, time_locale=None):
+        """
+        Return the day name of the Timestamp with specified locale.
+
+        Parameters
+        ----------
+        time_locale : string, default None (English locale)
+            locale determining the language in which to return the day name
+
+        Returns
+        -------
+        day_name : string
+        """
+        if time_locale is None:
+            names = DAYS_FULL
+        else:
+            names = get_locale_names('f_weekday', time_locale)
+        days = dict(enumerate(names))
+        return days[self.weekday()].capitalize()
+
+    def month_name(self, time_locale=None):
+        """
+        Return the month name of the Timestamp with specified locale.
+
+        Parameters
+        ----------
+        time_locale : string, default None (English locale)
+            locale determining the language in which to return the month name
+
+        Returns
+        -------
+        month_name : string
+        """
+        if time_locale is None:
+            names = MONTHS_FULL
+        else:
+            names = get_locale_names('f_month', time_locale)
+        months = dict(enumerate(names))
+        return months[self.month].capitalize()
+
     @property
     def weekday_name(self):
+        """
+        .. deprecated:: 0.23.0
+            Use ``Timestamp.day_name()`` instead
+        """
+        warnings.warn("`weekday_name` is deprecated and will be removed in a "
+                      "future version. Use `day_name` instead",
+                      DeprecationWarning)
         cdef dict wdays = {0: 'Monday', 1: 'Tuesday', 2: 'Wednesday',
                            3: 'Thursday', 4: 'Friday', 5: 'Saturday',
                            6: 'Sunday'}

pandas/core/indexes/datetimes.py

@@ -262,6 +262,8 @@ class DatetimeIndex(DatelikeOps, TimelikeOps, DatetimeIndexOpsMixin,
     to_pydatetime
     to_series
     to_frame
+    month_name
+    day_name
 
     Notes
     -----
@@ -1719,7 +1721,7 @@ def freq(self, value):
     weekday_name = _field_accessor(
         'weekday_name',
         'weekday_name',
-        "The name of day in a week (ex: Friday)\n\n.. versionadded:: 0.18.1")
+        "The name of day in a week (ex: Friday)\n\n.. deprecated:: 0.23.0")
 
     dayofyear = _field_accessor('dayofyear', 'doy',
                                 "The ordinal day of the year")
@@ -2103,6 +2105,54 @@ def to_julian_date(self):
                              self.nanosecond / 3600.0 / 1e+9
                              ) / 24.0)
 
+    def month_name(self, time_locale=None):
+        """
+        Return the month names of the DateTimeIndex with specified locale.
+
+        Parameters
+        ----------
+        time_locale : string, default None (English locale)
+            locale determining the language in which to return the month name
+
+        Returns
+        -------
+        month_names : Index
+            Index of month names
+        """
+        values = self.asi8
+        if self.tz is not None:
+            if self.tz is not utc:
+                values = self._local_timestamps()
+
+        result = fields.get_date_name_field(values, 'month_name',
+                                            time_locale=time_locale)
+        result = self._maybe_mask_results(result)
+        return Index(result, name=self.name)
+
+    def day_name(self, time_locale=None):
+        """
+        Return the day names of the DateTimeIndex with specified locale.
+
+        Parameters
+        ----------
+        time_locale : string, default None (English locale)
+            locale determining the language in which to return the day name
+
+        Returns
+        -------
+        month_names : Index
+            Index of day names
+        """
+        values = self.asi8
+        if self.tz is not None:
+            if self.tz is not utc:
+                values = self._local_timestamps()
+
+        result = fields.get_date_name_field(values, 'day_name',
+                                            time_locale=time_locale)
+        result = self._maybe_mask_results(result)
+        return Index(result, name=self.name)
+
 
 DatetimeIndex._add_comparison_methods()
 DatetimeIndex._add_numeric_methods_disabled()