BUG: GH29461 Strftime

asv_bench/benchmarks/timeseries.py

@@ -423,4 +423,23 @@ def time_dt_accessor_year(self, tz):
         self.series.dt.year
 
 
+class DateTimeAccessorStrftime:
+
+    params = (
+        [None, "US/Eastern", "UTC", dateutil.tz.tzutc()],
+        ["%Y-%m-%d %H:%M:%S.%f%z", "%Y-%m-%d %H:%M:%S%z"],
+        ["T", "S", "NS"],
+    )
+    param_names = ["tz", "fmt", "frequency"]
+
+    def setup(self, tz, fmt, frequency):
+        N = 100000
+        self.series = Series(
+            date_range(start="1/1/2000", periods=N, freq=frequency, tz=tz)
+        )
+
+    def time_dt_accessor_strftime(self, tz, fmt, frequency):
+        self.series.dt.strftime(fmt)
+
+
 from .pandas_vb_common import setup  # noqa: F401 isort:skip

asv_bench/benchmarks/tslibs/timestamp.py

@@ -120,6 +120,17 @@ def time_weekday_name(self, tz, freq):
         self.ts.day_name()
 
 
+class TimestampStrftimeMethod:
+    params = ["%Y-%m-%d %H:%M:%S", "%Y-%m-%d %H:%M:%S.%f"]
+    param_names = ["fmt"]
+
+    def setup(self, fmt):
+        self.ts = Timestamp("2020-05-23 18:06:13.123456789")
+
+    def time_strftime(self, fmt):
+        self.ts.strftime(fmt)
+
+
 class TimestampOps:
     params = _tzs
     param_names = ["tz"]

doc/source/whatsnew/v1.1.0.rst

@@ -915,6 +915,7 @@ Datetimelike
 - Bug in :meth:`DatetimeIndex.intersection` and :meth:`TimedeltaIndex.intersection` with results not having the correct ``name`` attribute (:issue:`33904`)
 - Bug in :meth:`DatetimeArray.__setitem__`, :meth:`TimedeltaArray.__setitem__`, :meth:`PeriodArray.__setitem__` incorrectly allowing values with ``int64`` dtype to be silently cast (:issue:`33717`)
 - Bug in subtracting :class:`TimedeltaIndex` from :class:`Period` incorrectly raising ``TypeError`` in some cases where it should succeed and ``IncompatibleFrequency`` in some cases where it should raise ``TypeError`` (:issue:`33883`)
+- Bug in :meth:`Timestamp.strftime` did not display full nanosecond precision (:issue:`29461`)
 - Bug in constructing a Series or Index from a read-only NumPy array with non-ns
   resolution which converted to object dtype instead of coercing to ``datetime64[ns]``
   dtype when within the timestamp bounds (:issue:`34843`).

pandas/_libs/tslibs/nattype.pyx

@@ -452,7 +452,25 @@ class NaTType(_NaT):
         Function is not implemented. Use pd.to_datetime().
         """,
     )
+    strftime = _make_error_func(
+        "strftime",
+        """
+        Constructs datetime style `format` string from Timestamp.
+
+        See `datetime <https://docs.python.org/3/library/datetime\
+.html#strftime-and-strptime-format-codes>`_ module for all available directives.
+
+        Parameters
+        ----------
+        format : str
+            String of formatting directives
 
+        Returns
+        -------
+        str
+            String representation of Timestamp
+        """,
+    )
     utcfromtimestamp = _make_error_func(
         "utcfromtimestamp",
         """

pandas/_libs/tslibs/timestamps.pyx

@@ -645,14 +645,10 @@ cdef class _Timestamp(ABCTimestamp):
 
     @property
     def _time_repr(self) -> str:
-        result = f'{self.hour:02d}:{self.minute:02d}:{self.second:02d}'
-
-        if self.nanosecond != 0:
-            result += f'.{self.nanosecond + 1000 * self.microsecond:09d}'
-        elif self.microsecond != 0:
-            result += f'.{self.microsecond:06d}'
-
-        return result
+        fmt = '%H:%M:%S'
+        if self.microsecond or self.nanosecond:
+            fmt = '%H:%M:%S.%f'
+        return self.strftime(fmt)
 
     @property
     def _short_repr(self) -> str:
@@ -1473,6 +1469,28 @@ default 'raise'
                  self.nanosecond / 3600.0 / 1e+9
                 ) / 24.0)
 
+    def strftime(self, format: str) -> str:
+        """
+        Constructs datetime style `format` string from Timestamp.
+
+        See `datetime <https://docs.python.org/3/library/datetime\
+.html#strftime-and-strptime-format-codes>`_ module for all available directives.
+
+        Parameters
+        ----------
+        format : str
+            String of formatting directives
+
+        Returns
+        -------
+        str
+            String representation of Timestamp
+        """
+        if self.nanosecond and '%f' in format:
+            replacement = f'{self.microsecond * 1000 + self.nanosecond:09d}'
+            format = format.replace('%f', replacement)
+        return super().strftime(format)
+
 
 # Aliases
 Timestamp.weekofyear = Timestamp.week

pandas/tests/scalar/timestamp/test_timestamp.py

@@ -15,7 +15,7 @@
 from pandas.compat.numpy import np_datetime64_compat
 import pandas.util._test_decorators as td
 
-from pandas import NaT, Timedelta, Timestamp
+from pandas import NaT, Timedelta, Timestamp, to_datetime
 import pandas._testing as tm
 
 from pandas.tseries import offsets
@@ -381,6 +381,55 @@ def test_tz_conversion_freq(self, tz_naive_fixture):
         t2 = Timestamp("2019-01-02 12:00", tz="UTC", freq="T")
         assert t2.tz_convert(tz="UTC").freq == t2.freq
 
+    @pytest.mark.parametrize(
+        "_input,fmt,_output",
+        [
+            ("2020-05-22 11:07:30", "%Y-%m-%d", "2020-05-22"),
+            ("2020-05-22 11:07:30.123456", "%Y-%m-%d %f", "2020-05-22 123456"),
+            ("2020-05-22 11:07:30.123456789", "%f", "123456789"),
+        ],
+    )
+    def test_strftime(self, _input, fmt, _output):
+        ts = Timestamp(_input)
+        result = ts.strftime(fmt)
+        assert result == _output
+
+    @pytest.mark.parametrize(
+        "fmt",
+        [
+            "%a",
+            "%A",
+            "%w",
+            "%d",
+            "%b",
+            "%B",
+            "%m",
+            "%y",
+            "%Y",
+            "%H",
+            "%I",
+            "%p",
+            "%M",
+            "%S",
+            "%f",
+            "%z",
+            "%Z",
+            "%j",
+            "%U",
+            "%W",
+            "%c",
+            "%x",
+            "%X",
+            "%G",
+            "%u",
+            "%V",
+        ],
+    )
+    def test_strftime_components(self, fmt):
+        ts = Timestamp("2020-06-09 09:04:11.123456", tzinfo=utc)
+        dt = datetime(2020, 6, 9, 9, 4, 11, 123456, tzinfo=utc)
+        assert ts.strftime(fmt) == dt.strftime(fmt)
+
 
 class TestTimestampNsOperations:
     def test_nanosecond_string_parsing(self):
@@ -442,6 +491,20 @@ def test_nanosecond_timestamp(self):
         assert t.value == expected
         assert t.nanosecond == 10
 
+    @pytest.mark.parametrize(
+        "date",
+        [
+            "2020-05-22 08:53:19.123456789",
+            "2020-05-22 08:53:19.123456",
+            "2020-05-22 08:53:19",
+        ],
+    )
+    @pytest.mark.parametrize("fmt", ["%m/%d/%Y %H:%M:%S.%f", "%m%d%Y%H%M%S%f"])
+    def test_nanosecond_roundtrip(self, date, fmt):
+        ts = Timestamp(date)
+        string = ts.strftime(fmt)
+        assert ts == to_datetime(string, format=fmt)
+
 
 class TestTimestampToJulianDate:
     def test_compare_1700(self):