From 3728a70a01639589e5bd1efa14f509a0ea2f2446 Mon Sep 17 00:00:00 2001
From: MomIsBestFriend <50263213+MomIsBestFriend@users.noreply.github.com>
Date: Fri, 22 Nov 2019 17:32:43 +0200
Subject: [PATCH] CLN:F-string in pandas/_libs/tslibs/*.pyx (#29775)

---
 pandas/_libs/tslibs/c_timestamp.pyx  | 24 +++++-----
 pandas/_libs/tslibs/conversion.pyx   |  8 ++--
 pandas/_libs/tslibs/fields.pyx       | 11 +++--
 pandas/_libs/tslibs/frequencies.pyx  |  2 +-
 pandas/_libs/tslibs/nattype.pyx      | 12 +++--
 pandas/_libs/tslibs/np_datetime.pyx  |  8 ++--
 pandas/_libs/tslibs/offsets.pyx      | 19 ++++----
 pandas/_libs/tslibs/parsing.pyx      | 26 +++++------
 pandas/_libs/tslibs/period.pyx       | 44 +++++++++---------
 pandas/_libs/tslibs/strptime.pyx     | 32 +++++++------
 pandas/_libs/tslibs/timedeltas.pyx   | 67 +++++++++++-----------------
 pandas/_libs/tslibs/timestamps.pyx   | 12 ++---
 pandas/_libs/tslibs/timezones.pyx    |  4 +-
 pandas/_libs/tslibs/tzconversion.pyx | 16 +++----
 14 files changed, 127 insertions(+), 158 deletions(-)

diff --git a/pandas/_libs/tslibs/c_timestamp.pyx b/pandas/_libs/tslibs/c_timestamp.pyx
index 8512b34b9e78cc..c6c98e996b7457 100644
--- a/pandas/_libs/tslibs/c_timestamp.pyx
+++ b/pandas/_libs/tslibs/c_timestamp.pyx
@@ -55,11 +55,11 @@ def maybe_integer_op_deprecated(obj):
     # GH#22535 add/sub of integers and int-arrays is deprecated
     if obj.freq is not None:
         warnings.warn("Addition/subtraction of integers and integer-arrays "
-                      "to {cls} is deprecated, will be removed in a future "
+                      f"to {type(obj).__name__} is deprecated, "
+                      "will be removed in a future "
                       "version.  Instead of adding/subtracting `n`, use "
                       "`n * self.freq`"
-                      .format(cls=type(obj).__name__),
-                      FutureWarning)
+                      , FutureWarning)
 
 
 cdef class _Timestamp(datetime):
@@ -144,11 +144,10 @@ cdef class _Timestamp(datetime):
             # e.g. tzlocal has no `strftime`
             pass
 
-        tz = ", tz='{0}'".format(zone) if zone is not None else ""
-        freq = "" if self.freq is None else ", freq='{0}'".format(self.freqstr)
+        tz = f", tz='{zone}'" if zone is not None else ""
+        freq = "" if self.freq is None else f", freq='{self.freqstr}'"
 
-        return "Timestamp('{stamp}'{tz}{freq})".format(stamp=stamp,
-                                                       tz=tz, freq=freq)
+        return f"Timestamp('{stamp}'{tz}{freq})"
 
     cdef bint _compare_outside_nanorange(_Timestamp self, datetime other,
                                          int op) except -1:
@@ -370,23 +369,22 @@ cdef class _Timestamp(datetime):
 
     @property
     def _repr_base(self) -> str:
-        return '{date} {time}'.format(date=self._date_repr,
-                                      time=self._time_repr)
+        return f"{self._date_repr} {self._time_repr}"
 
     @property
     def _date_repr(self) -> str:
         # Ideal here would be self.strftime("%Y-%m-%d"), but
         # the datetime strftime() methods require year >= 1900
-        return '%d-%.2d-%.2d' % (self.year, self.month, self.day)
+        return f'{self.year}-{self.month:02d}-{self.day:02d}'
 
     @property
     def _time_repr(self) -> str:
-        result = '%.2d:%.2d:%.2d' % (self.hour, self.minute, self.second)
+        result = f'{self.hour:02d}:{self.minute:02d}:{self.second:02d}'
 
         if self.nanosecond != 0:
-            result += '.%.9d' % (self.nanosecond + 1000 * self.microsecond)
+            result += f'.{self.nanosecond + 1000 * self.microsecond:09d}'
         elif self.microsecond != 0:
-            result += '.%.6d' % self.microsecond
+            result += f'.{self.microsecond:06d}'
 
         return result
 
diff --git a/pandas/_libs/tslibs/conversion.pyx b/pandas/_libs/tslibs/conversion.pyx
index bd74180403ad9f..c5315219b8422c 100644
--- a/pandas/_libs/tslibs/conversion.pyx
+++ b/pandas/_libs/tslibs/conversion.pyx
@@ -197,7 +197,7 @@ def datetime_to_datetime64(object[:] values):
                 iresult[i] = pydatetime_to_dt64(val, &dts)
                 check_dts_bounds(&dts)
         else:
-            raise TypeError('Unrecognized value type: %s' % type(val))
+            raise TypeError(f'Unrecognized value type: {type(val)}')
 
     return result, inferred_tz
 
@@ -326,8 +326,8 @@ cdef convert_to_tsobject(object ts, object tz, object unit,
         raise ValueError("Cannot convert Period to Timestamp "
                          "unambiguously. Use to_timestamp")
     else:
-        raise TypeError('Cannot convert input [{}] of type {} to '
-                        'Timestamp'.format(ts, type(ts)))
+        raise TypeError(f'Cannot convert input [{ts}] of type {type(ts)} to '
+                        f'Timestamp')
 
     if tz is not None:
         localize_tso(obj, tz)
@@ -686,7 +686,7 @@ def normalize_date(dt: object) -> datetime:
     elif PyDate_Check(dt):
         return datetime(dt.year, dt.month, dt.day)
     else:
-        raise TypeError('Unrecognized type: %s' % type(dt))
+        raise TypeError(f'Unrecognized type: {type(dt)}')
 
 
 @cython.wraparound(False)
diff --git a/pandas/_libs/tslibs/fields.pyx b/pandas/_libs/tslibs/fields.pyx
index 8f5c8d10776dfd..dfed8d06530aa7 100644
--- a/pandas/_libs/tslibs/fields.pyx
+++ b/pandas/_libs/tslibs/fields.pyx
@@ -130,7 +130,7 @@ def get_date_name_field(const int64_t[:] dtindex, object field, object locale=No
             out[i] = names[dts.month].capitalize()
 
     else:
-        raise ValueError("Field {field} not supported".format(field=field))
+        raise ValueError(f"Field {field} not supported")
 
     return out
 
@@ -165,8 +165,7 @@ def get_start_end_field(const int64_t[:] dtindex, object field,
 
     if freqstr:
         if freqstr == 'C':
-            raise ValueError("Custom business days is not supported by {field}"
-                             .format(field=field))
+            raise ValueError(f"Custom business days is not supported by {field}")
         is_business = freqstr[0] == 'B'
 
         # YearBegin(), BYearBegin() use month = starting month of year.
@@ -373,7 +372,7 @@ def get_start_end_field(const int64_t[:] dtindex, object field,
                     out[i] = 1
 
     else:
-        raise ValueError("Field {field} not supported".format(field=field))
+        raise ValueError(f"Field {field} not supported")
 
     return out.view(bool)
 
@@ -537,7 +536,7 @@ def get_date_field(const int64_t[:] dtindex, object field):
     elif field == 'is_leap_year':
         return isleapyear_arr(get_date_field(dtindex, 'Y'))
 
-    raise ValueError("Field {field} not supported".format(field=field))
+    raise ValueError(f"Field {field} not supported")
 
 
 @cython.wraparound(False)
@@ -653,7 +652,7 @@ def get_timedelta_field(const int64_t[:] tdindex, object field):
                 out[i] = tds.nanoseconds
         return out
 
-    raise ValueError("Field %s not supported" % field)
+    raise ValueError(f"Field {field} not supported")
 
 
 cpdef isleapyear_arr(ndarray years):
diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index b29c8418960720..660f4ddcec7368 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -197,7 +197,7 @@ cpdef _base_and_stride(str freqstr):
     groups = opattern.match(freqstr)
 
     if not groups:
-        raise ValueError("Could not evaluate {freq}".format(freq=freqstr))
+        raise ValueError(f"Could not evaluate {freqstr}")
 
     stride = groups.group(1)
 
diff --git a/pandas/_libs/tslibs/nattype.pyx b/pandas/_libs/tslibs/nattype.pyx
index 3ddce28fb6dd16..6e5e62e77b4b1e 100644
--- a/pandas/_libs/tslibs/nattype.pyx
+++ b/pandas/_libs/tslibs/nattype.pyx
@@ -115,8 +115,8 @@ cdef class _NaT(datetime):
             if is_datetime64_object(other):
                 return _nat_scalar_rules[op]
             else:
-                raise TypeError('Cannot compare type %r with type %r' %
-                                (type(self).__name__, type(other).__name__))
+                raise TypeError(f'Cannot compare type {type(self).__name__} '
+                                f'with type {type(other).__name__}')
 
         # Note: instead of passing "other, self, _reverse_ops[op]", we observe
         # that `_nat_scalar_rules` is invariant under `_reverse_ops`,
@@ -150,8 +150,7 @@ cdef class _NaT(datetime):
                 result = np.empty(other.shape, dtype="datetime64[ns]")
                 result.fill("NaT")
                 return result
-            raise TypeError("Cannot add NaT to ndarray with dtype {dtype}"
-                            .format(dtype=other.dtype))
+            raise TypeError(f"Cannot add NaT to ndarray with dtype {other.dtype}")
 
         return NotImplemented
 
@@ -203,9 +202,8 @@ cdef class _NaT(datetime):
                 result.fill("NaT")
                 return result
 
-            raise TypeError(
-                "Cannot subtract NaT from ndarray with dtype {dtype}"
-                .format(dtype=other.dtype))
+            raise TypeError(f"Cannot subtract NaT from ndarray with "
+                            f"dtype {other.dtype}")
 
         return NotImplemented
 
diff --git a/pandas/_libs/tslibs/np_datetime.pyx b/pandas/_libs/tslibs/np_datetime.pyx
index e76f84265a327b..b9406074bb130b 100644
--- a/pandas/_libs/tslibs/np_datetime.pyx
+++ b/pandas/_libs/tslibs/np_datetime.pyx
@@ -112,11 +112,9 @@ cdef inline check_dts_bounds(npy_datetimestruct *dts):
         error = True
 
     if error:
-        fmt = '%d-%.2d-%.2d %.2d:%.2d:%.2d' % (dts.year, dts.month,
-                                               dts.day, dts.hour,
-                                               dts.min, dts.sec)
-        raise OutOfBoundsDatetime(
-            'Out of bounds nanosecond timestamp: {fmt}'.format(fmt=fmt))
+        fmt = (f'{dts.year}-{dts.month:02d}-{dts.day:02d} '
+               f'{dts.hour:02d}:{dts.min:02d}:{dts.sec:02d}')
+        raise OutOfBoundsDatetime(f'Out of bounds nanosecond timestamp: {fmt}')
 
 
 # ----------------------------------------------------------------------
diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 434252677f1a1b..68a0a4a403c817 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -66,16 +66,16 @@ need_suffix = ['QS', 'BQ', 'BQS', 'YS', 'AS', 'BY', 'BA', 'BYS', 'BAS']
 
 for __prefix in need_suffix:
     for _m in MONTHS:
-        key = '%s-%s' % (__prefix, _m)
+        key = f'{__prefix}-{_m}'
         _offset_to_period_map[key] = _offset_to_period_map[__prefix]
 
 for __prefix in ['A', 'Q']:
     for _m in MONTHS:
-        _alias = '%s-%s' % (__prefix, _m)
+        _alias = f'{__prefix}-{_m}'
         _offset_to_period_map[_alias] = _alias
 
 for _d in DAYS:
-    _offset_to_period_map['W-%s' % _d] = 'W-%s' % _d
+    _offset_to_period_map[f'W-{_d}'] = f'W-{_d}'
 
 
 # ---------------------------------------------------------------------
@@ -432,9 +432,9 @@ class _BaseOffset:
 
         n_str = ""
         if self.n != 1:
-            n_str = "%s * " % self.n
+            n_str = f"{self.n} * "
 
-        out = '<%s' % n_str + className + plural + self._repr_attrs() + '>'
+        out = f'<{n_str}{className}{plural}{self._repr_attrs()}>'
         return out
 
     def _get_offset_day(self, datetime other):
@@ -460,16 +460,13 @@ class _BaseOffset:
         ValueError if n != int(n)
         """
         if util.is_timedelta64_object(n):
-            raise TypeError('`n` argument must be an integer, '
-                            'got {ntype}'.format(ntype=type(n)))
+            raise TypeError(f'`n` argument must be an integer, got {type(n)}')
         try:
             nint = int(n)
         except (ValueError, TypeError):
-            raise TypeError('`n` argument must be an integer, '
-                            'got {ntype}'.format(ntype=type(n)))
+            raise TypeError(f'`n` argument must be an integer, got {type(n)}')
         if n != nint:
-            raise ValueError('`n` argument must be an integer, '
-                             'got {n}'.format(n=n))
+            raise ValueError(f'`n` argument must be an integer, got {n}')
         return nint
 
     def __setstate__(self, state):
diff --git a/pandas/_libs/tslibs/parsing.pyx b/pandas/_libs/tslibs/parsing.pyx
index 8fe724fa2f6f7d..ecf3e35c86d768 100644
--- a/pandas/_libs/tslibs/parsing.pyx
+++ b/pandas/_libs/tslibs/parsing.pyx
@@ -153,7 +153,7 @@ cdef inline object _parse_delimited_date(object date_string, bint dayfirst):
             return datetime_new(year, month, day, 0, 0, 0, 0, None), reso
         return datetime(year, month, day, 0, 0, 0, 0, None), reso
 
-    raise DateParseError("Invalid date specified ({}/{})".format(month, day))
+    raise DateParseError(f"Invalid date specified ({month}/{day})")
 
 
 cdef inline bint does_string_look_like_time(object parse_string):
@@ -311,7 +311,7 @@ cdef parse_datetime_string_with_reso(date_string, freq=None, dayfirst=False,
         # TODO: allow raise of errors within instead
         raise DateParseError(err)
     if parsed is None:
-        raise DateParseError("Could not parse {dstr}".format(dstr=date_string))
+        raise DateParseError(f"Could not parse {date_string}")
     return parsed, parsed, reso
 
 
@@ -420,18 +420,18 @@ cdef inline object _parse_dateabbr_string(object date_string, object default,
                     raise ValueError
 
             if not (1 <= quarter <= 4):
-                msg = ('Incorrect quarterly string is given, quarter must be '
-                       'between 1 and 4: {dstr}')
-                raise DateParseError(msg.format(dstr=date_string))
+                raise DateParseError(f'Incorrect quarterly string is given, '
+                                     f'quarter must be '
+                                     f'between 1 and 4: {date_string}')
 
             if freq is not None:
                 # hack attack, #1228
                 try:
                     mnum = MONTH_NUMBERS[_get_rule_month(freq)] + 1
                 except (KeyError, ValueError):
-                    msg = ('Unable to retrieve month information from given '
-                           'freq: {freq}'.format(freq=freq))
-                    raise DateParseError(msg)
+                    raise DateParseError(f'Unable to retrieve month '
+                                         f'information from given '
+                                         f'freq: {freq}')
 
                 month = (mnum + (quarter - 1) * 3) % 12 + 1
                 if month > mnum:
@@ -464,7 +464,7 @@ cdef inline object _parse_dateabbr_string(object date_string, object default,
         except ValueError:
             pass
 
-    raise ValueError('Unable to parse {0}'.format(date_string))
+    raise ValueError(f'Unable to parse {date_string}')
 
 
 cdef dateutil_parse(object timestr, object default, ignoretz=False,
@@ -484,8 +484,7 @@ cdef dateutil_parse(object timestr, object default, ignoretz=False,
         res, _ = res
 
     if res is None:
-        msg = "Unknown datetime string format, unable to parse: {timestr}"
-        raise ValueError(msg.format(timestr=timestr))
+        raise ValueError(f"Unknown datetime string format, unable to parse: {timestr}")
 
     for attr in ["year", "month", "day", "hour",
                  "minute", "second", "microsecond"]:
@@ -495,8 +494,7 @@ cdef dateutil_parse(object timestr, object default, ignoretz=False,
             reso = attr
 
     if reso is None:
-        msg = "Unable to parse datetime string: {timestr}"
-        raise ValueError(msg.format(timestr=timestr))
+        raise ValueError(f"Unable to parse datetime string: {timestr}")
 
     if reso == 'microsecond':
         if repl['microsecond'] == 0:
@@ -710,7 +708,7 @@ class _timelex:
         elif getattr(instream, 'read', None) is None:
             raise TypeError(
                 'Parser must be a string or character stream, not '
-                '{itype}'.format(itype=instream.__class__.__name__))
+                f'{type(instream).__name__}')
         else:
             self.stream = instream.read()
 
diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
index 2512fdb891e3ea..80db081a4fc52d 100644
--- a/pandas/_libs/tslibs/period.pyx
+++ b/pandas/_libs/tslibs/period.pyx
@@ -1227,7 +1227,7 @@ def period_format(int64_t value, int freq, object fmt=None):
         elif freq_group == 12000:  # NANOSEC
             fmt = b'%Y-%m-%d %H:%M:%S.%n'
         else:
-            raise ValueError('Unknown freq: {freq}'.format(freq=freq))
+            raise ValueError(f'Unknown freq: {freq}')
 
     return _period_strftime(value, freq, fmt)
 
@@ -1273,17 +1273,17 @@ cdef object _period_strftime(int64_t value, int freq, object fmt):
                 raise ValueError('Unable to get quarter and year')
 
             if i == 0:
-                repl = '%d' % quarter
+                repl = str(quarter)
             elif i == 1:  # %f, 2-digit year
-                repl = '%.2d' % (year % 100)
+                repl = f'{(year % 100):02d}'
             elif i == 2:
-                repl = '%d' % year
+                repl = str(year)
             elif i == 3:
-                repl = '%03d' % (value % 1000)
+                repl = f'{(value % 1_000):03d}'
             elif i == 4:
-                repl = '%06d' % (value % 1000000)
+                repl = f'{(value % 1_000_000):06d}'
             elif i == 5:
-                repl = '%09d' % (value % 1000000000)
+                repl = f'{(value % 1_000_000_000):09d}'
 
             result = result.replace(str_extra_fmts[i], repl)
 
@@ -1391,7 +1391,7 @@ def get_period_field_arr(int code, int64_t[:] arr, int freq):
 
     func = _get_accessor_func(code)
     if func is NULL:
-        raise ValueError('Unrecognized period code: {code}'.format(code=code))
+        raise ValueError(f'Unrecognized period code: {code}')
 
     sz = len(arr)
     out = np.empty(sz, dtype=np.int64)
@@ -1578,9 +1578,8 @@ cdef class _Period:
         freq = to_offset(freq)
 
         if freq.n <= 0:
-            raise ValueError('Frequency must be positive, because it'
-                             ' represents span: {freqstr}'
-                             .format(freqstr=freq.freqstr))
+            raise ValueError(f'Frequency must be positive, because it '
+                             f'represents span: {freq.freqstr}')
 
         return freq
 
@@ -1614,9 +1613,8 @@ cdef class _Period:
                 return NotImplemented
             elif op == Py_NE:
                 return NotImplemented
-            raise TypeError('Cannot compare type {cls} with type {typ}'
-                            .format(cls=type(self).__name__,
-                                    typ=type(other).__name__))
+            raise TypeError(f'Cannot compare type {type(self).__name__} '
+                            f'with type {type(other).__name__}')
 
     def __hash__(self):
         return hash((self.ordinal, self.freqstr))
@@ -1634,8 +1632,8 @@ cdef class _Period:
                 if nanos % offset_nanos == 0:
                     ordinal = self.ordinal + (nanos // offset_nanos)
                     return Period(ordinal=ordinal, freq=self.freq)
-            msg = 'Input cannot be converted to Period(freq={0})'
-            raise IncompatibleFrequency(msg.format(self.freqstr))
+            raise IncompatibleFrequency(f'Input cannot be converted to '
+                                        f'Period(freq={self.freqstr})')
         elif util.is_offset_object(other):
             freqstr = other.rule_code
             base = get_base_alias(freqstr)
@@ -1665,9 +1663,8 @@ cdef class _Period:
                 # GH#17983
                 sname = type(self).__name__
                 oname = type(other).__name__
-                raise TypeError("unsupported operand type(s) for +: '{self}' "
-                                "and '{other}'".format(self=sname,
-                                                       other=oname))
+                raise TypeError(f"unsupported operand type(s) for +: '{sname}' "
+                                f"and '{oname}'")
             else:  # pragma: no cover
                 return NotImplemented
         elif is_period_object(other):
@@ -2218,7 +2215,7 @@ cdef class _Period:
     def __repr__(self) -> str:
         base, mult = get_freq_code(self.freq)
         formatted = period_format(self.ordinal, base)
-        return "Period('%s', '%s')" % (formatted, self.freqstr)
+        return f"Period('{formatted}', '{self.freqstr}')"
 
     def __str__(self) -> str:
         """
@@ -2226,7 +2223,7 @@ cdef class _Period:
         """
         base, mult = get_freq_code(self.freq)
         formatted = period_format(self.ordinal, base)
-        value = ("%s" % formatted)
+        value = str(formatted)
         return value
 
     def __setstate__(self, state):
@@ -2477,9 +2474,8 @@ class Period(_Period):
                 try:
                     freq = Resolution.get_freq(reso)
                 except KeyError:
-                    raise ValueError(
-                        "Invalid frequency or could not infer: {reso}"
-                        .format(reso=reso))
+                    raise ValueError(f"Invalid frequency or could not "
+                                     f"infer: {reso}")
 
         elif PyDateTime_Check(value):
             dt = value
diff --git a/pandas/_libs/tslibs/strptime.pyx b/pandas/_libs/tslibs/strptime.pyx
index fbda5f178e1647..71e50067610978 100644
--- a/pandas/_libs/tslibs/strptime.pyx
+++ b/pandas/_libs/tslibs/strptime.pyx
@@ -106,11 +106,11 @@ def array_strptime(object[:] values, object fmt,
                 if bad_directive == "\\":
                     bad_directive = "%"
                 del err
-                raise ValueError("'%s' is a bad directive in format '%s'" %
-                                 (bad_directive, fmt))
+                raise ValueError(f"'{bad_directive}' is a bad directive "
+                                 f"in format '{fmt}'")
             # IndexError only occurs when the format string is "%"
             except IndexError:
-                raise ValueError("stray %% in format '%s'" % fmt)
+                raise ValueError("stray % in format '{fmt}'")
             _regex_cache[fmt] = format_regex
 
     result = np.empty(n, dtype='M8[ns]')
@@ -139,14 +139,13 @@ def array_strptime(object[:] values, object fmt,
                 if is_coerce:
                     iresult[i] = NPY_NAT
                     continue
-                raise ValueError("time data %r does not match "
-                                 "format %r (match)" % (val, fmt))
+                raise ValueError(f"time data '{val}' does not match "
+                                 f"format '{fmt}' (match)")
             if len(val) != found.end():
                 if is_coerce:
                     iresult[i] = NPY_NAT
                     continue
-                raise ValueError("unconverted data remains: %s" %
-                                 val[found.end():])
+                raise ValueError(f"unconverted data remains: {val[found.end():]}")
 
         # search
         else:
@@ -155,8 +154,8 @@ def array_strptime(object[:] values, object fmt,
                 if is_coerce:
                     iresult[i] = NPY_NAT
                     continue
-                raise ValueError("time data %r does not match format "
-                                 "%r (search)" % (val, fmt))
+                raise ValueError(f"time data {repr(val)} does not match format "
+                                 f"{repr(fmt)} (search)")
 
         iso_year = -1
         year = 1900
@@ -589,8 +588,8 @@ class TimeRE(dict):
         else:
             return ''
         regex = '|'.join(re.escape(stuff) for stuff in to_convert)
-        regex = '(?P<%s>%s' % (directive, regex)
-        return '%s)' % regex
+        regex = f'(?P<{directive}>{regex})'
+        return regex
 
     def pattern(self, format):
         """
@@ -609,11 +608,11 @@ class TimeRE(dict):
         format = whitespace_replacement.sub(r'\\s+', format)
         while '%' in format:
             directive_index = format.index('%') +1
-            processed_format = "%s%s%s" % (processed_format,
-                                           format[:directive_index -1],
-                                           self[format[directive_index]])
+            processed_format = (f"{processed_format}"
+                                f"{format[:directive_index -1]}"
+                                f"{self[format[directive_index]]}")
             format = format[directive_index +1:]
-        return "%s%s" % (processed_format, format)
+        return f"{processed_format}{format}"
 
     def compile(self, format):
         """Return a compiled re object for the format string."""
@@ -737,8 +736,7 @@ cdef parse_timezone_directive(str z):
         z = z[:3] + z[4:]
         if len(z) > 5:
             if z[5] != ':':
-                msg = "Inconsistent use of : in {0}"
-                raise ValueError(msg.format(z))
+                raise ValueError(f"Inconsistent use of : in {z}")
             z = z[:5] + z[6:]
     hours = int(z[1:3])
     minutes = int(z[3:5])
diff --git a/pandas/_libs/tslibs/timedeltas.pyx b/pandas/_libs/tslibs/timedeltas.pyx
index 21dbdfbb111ed5..8e5b7197498578 100644
--- a/pandas/_libs/tslibs/timedeltas.pyx
+++ b/pandas/_libs/tslibs/timedeltas.pyx
@@ -170,7 +170,7 @@ cdef convert_to_timedelta64(object ts, object unit):
         if ts.astype('int64') == NPY_NAT:
             return np.timedelta64(NPY_NAT)
     elif is_timedelta64_object(ts):
-        ts = ts.astype("m8[{unit}]".format(unit=unit.lower()))
+        ts = ts.astype(f"m8[{unit.lower()}]")
     elif is_integer_object(ts):
         if ts == NPY_NAT:
             return np.timedelta64(NPY_NAT)
@@ -198,8 +198,7 @@ cdef convert_to_timedelta64(object ts, object unit):
     if PyDelta_Check(ts):
         ts = np.timedelta64(delta_to_nanoseconds(ts), 'ns')
     elif not is_timedelta64_object(ts):
-        raise ValueError("Invalid type for timedelta "
-                         "scalar: {ts_type}".format(ts_type=type(ts)))
+        raise ValueError(f"Invalid type for timedelta scalar: {type(ts)}")
     return ts.astype('timedelta64[ns]')
 
 
@@ -288,7 +287,7 @@ cpdef inline object precision_from_unit(object unit):
         m = 1L
         p = 0
     else:
-        raise ValueError("cannot cast unit {unit}".format(unit=unit))
+        raise ValueError(f"cannot cast unit {unit}")
     return m, p
 
 
@@ -397,8 +396,7 @@ cdef inline int64_t parse_timedelta_string(str ts) except? -1:
                 result += timedelta_as_neg(r, neg)
                 have_hhmmss = 1
             else:
-                raise ValueError("expecting hh:mm:ss format, "
-                                 "received: {ts}".format(ts=ts))
+                raise ValueError(f"expecting hh:mm:ss format, received: {ts}")
 
             unit, number = [], []
 
@@ -511,7 +509,7 @@ cdef inline timedelta_from_spec(object number, object frac, object unit):
             unit = 'm'
         unit = parse_timedelta_unit(unit)
     except KeyError:
-        raise ValueError("invalid abbreviation: {unit}".format(unit=unit))
+        raise ValueError(f"invalid abbreviation: {unit}")
 
     n = ''.join(number) + '.' + ''.join(frac)
     return cast_from_unit(float(n), unit)
@@ -530,8 +528,7 @@ cpdef inline object parse_timedelta_unit(object unit):
     try:
         return timedelta_abbrevs[unit.lower()]
     except (KeyError, AttributeError):
-        raise ValueError("invalid unit abbreviation: {unit}"
-                         .format(unit=unit))
+        raise ValueError(f"invalid unit abbreviation: {unit}")
 
 # ----------------------------------------------------------------------
 # Timedelta ops utilities
@@ -727,8 +724,7 @@ cdef _to_py_int_float(v):
         return int(v)
     elif is_float_object(v):
         return float(v)
-    raise TypeError("Invalid type {typ}. Must be int or "
-                    "float.".format(typ=type(v)))
+    raise TypeError(f"Invalid type {type(v)}. Must be int or float.")
 
 
 # Similar to Timestamp/datetime, this is a construction requirement for
@@ -773,10 +769,9 @@ cdef class _Timedelta(timedelta):
                         elif op == Py_NE:
                             return True
                         # only allow ==, != ops
-                        raise TypeError('Cannot compare type {cls} with '
-                                        'type {other}'
-                                        .format(cls=type(self).__name__,
-                                                other=type(other).__name__))
+                        raise TypeError(f'Cannot compare type '
+                                        f'{type(self).__name__} with '
+                                        f'type {type(other).__name__}')
                 if util.is_array(other):
                     return PyObject_RichCompare(np.array([self]), other, op)
                 return PyObject_RichCompare(other, self, reverse_ops[op])
@@ -787,10 +782,8 @@ cdef class _Timedelta(timedelta):
                     return False
                 elif op == Py_NE:
                     return True
-                raise TypeError('Cannot compare type {cls} with '
-                                'type {other}'
-                                .format(cls=type(self).__name__,
-                                        other=type(other).__name__))
+                raise TypeError(f'Cannot compare type {type(self).__name__} with '
+                                f'type {type(other).__name__}')
 
         return cmp_scalar(self.value, ots.value, op)
 
@@ -1143,7 +1136,8 @@ cdef class _Timedelta(timedelta):
         return fmt.format(**comp_dict)
 
     def __repr__(self) -> str:
-        return "Timedelta('{val}')".format(val=self._repr_base(format='long'))
+        repr_based = self._repr_base(format='long')
+        return f"Timedelta('{repr_based}')"
 
     def __str__(self) -> str:
         return self._repr_base(format='long')
@@ -1189,14 +1183,14 @@ cdef class _Timedelta(timedelta):
         'P500DT12H0MS'
         """
         components = self.components
-        seconds = '{}.{:0>3}{:0>3}{:0>3}'.format(components.seconds,
-                                                 components.milliseconds,
-                                                 components.microseconds,
-                                                 components.nanoseconds)
+        seconds = (f'{components.seconds}.'
+                   f'{components.milliseconds:0>3}'
+                   f'{components.microseconds:0>3}'
+                   f'{components.nanoseconds:0>3}')
         # Trim unnecessary 0s, 1.000000000 -> 1
         seconds = seconds.rstrip('0').rstrip('.')
-        tpl = ('P{td.days}DT{td.hours}H{td.minutes}M{seconds}S'
-               .format(td=components, seconds=seconds))
+        tpl = (f'P{components.days}DT{components.hours}'
+               f'H{components.minutes}M{seconds}S')
         return tpl
 
 
@@ -1276,7 +1270,7 @@ class Timedelta(_Timedelta):
             value = convert_to_timedelta64(value, 'ns')
         elif is_timedelta64_object(value):
             if unit is not None:
-                value = value.astype('timedelta64[{0}]'.format(unit))
+                value = value.astype(f'timedelta64[{unit}]')
             value = value.astype('timedelta64[ns]')
         elif hasattr(value, 'delta'):
             value = np.timedelta64(delta_to_nanoseconds(value.delta), 'ns')
@@ -1288,9 +1282,8 @@ class Timedelta(_Timedelta):
             return NaT
         else:
             raise ValueError(
-                "Value must be Timedelta, string, integer, "
-                "float, timedelta or convertible, not {typ}"
-                .format(typ=type(value).__name__))
+                f"Value must be Timedelta, string, integer, "
+                f"float, timedelta or convertible, not {type(value).__name__}")
 
         if is_timedelta64_object(value):
             value = value.view('i8')
@@ -1485,9 +1478,7 @@ class Timedelta(_Timedelta):
                 else:
                     return self.to_timedelta64() // other
 
-            raise TypeError('Invalid dtype {dtype} for '
-                            '{op}'.format(dtype=other.dtype,
-                                          op='__floordiv__'))
+            raise TypeError(f'Invalid dtype {other.dtype} for __floordiv__')
 
         elif is_integer_object(other) or is_float_object(other):
             return Timedelta(self.value // other, unit='ns')
@@ -1530,9 +1521,7 @@ class Timedelta(_Timedelta):
                 """)
                 warnings.warn(msg, FutureWarning)
                 return other // self.value
-            raise TypeError('Invalid dtype {dtype} for '
-                            '{op}'.format(dtype=other.dtype,
-                                          op='__floordiv__'))
+            raise TypeError(f'Invalid dtype {other.dtype} for __floordiv__')
 
         elif is_float_object(other) and util.is_nan(other):
             # i.e. np.nan
@@ -1555,8 +1544,7 @@ class Timedelta(_Timedelta):
         if hasattr(other, 'dtype') and other.dtype.kind == 'i':
             # TODO: Remove this check with backwards-compat shim
             # for integer / Timedelta is removed.
-            raise TypeError("Invalid type {dtype} for "
-                            "{op}".format(dtype=other.dtype, op='__mod__'))
+            raise TypeError(f'Invalid dtype {other.dtype} for __mod__')
         return self.__rdivmod__(other)[1]
 
     def __divmod__(self, other):
@@ -1569,8 +1557,7 @@ class Timedelta(_Timedelta):
         if hasattr(other, 'dtype') and other.dtype.kind == 'i':
             # TODO: Remove this check with backwards-compat shim
             # for integer / Timedelta is removed.
-            raise TypeError("Invalid type {dtype} for "
-                            "{op}".format(dtype=other.dtype, op='__mod__'))
+            raise TypeError(f'Invalid dtype {other.dtype} for __mod__')
         div = other // self
         return div, other - div * self
 
diff --git a/pandas/_libs/tslibs/timestamps.pyx b/pandas/_libs/tslibs/timestamps.pyx
index 03ed26337d539f..1a278f46a4a2ba 100644
--- a/pandas/_libs/tslibs/timestamps.pyx
+++ b/pandas/_libs/tslibs/timestamps.pyx
@@ -370,8 +370,8 @@ class Timestamp(_Timestamp):
         if tzinfo is not None:
             if not PyTZInfo_Check(tzinfo):
                 # tzinfo must be a datetime.tzinfo object, GH#17690
-                raise TypeError('tzinfo must be a datetime.tzinfo object, '
-                                'not %s' % type(tzinfo))
+                raise TypeError(f'tzinfo must be a datetime.tzinfo object, '
+                                f'not {type(tzinfo)}')
             elif tz is not None:
                 raise ValueError('Can provide at most one of tz, tzinfo')
 
@@ -946,8 +946,8 @@ default 'raise'
         def validate(k, v):
             """ validate integers """
             if not is_integer_object(v):
-                raise ValueError("value must be an integer, received "
-                                 "{v} for {k}".format(v=type(v), k=k))
+                raise ValueError(f"value must be an integer, received "
+                                 f"{type(v)} for {k}")
             return v
 
         if year is not None:
@@ -1003,9 +1003,9 @@ default 'raise'
             base1, base2 = base, ""
 
         if self.microsecond != 0:
-            base1 += "%.3d" % self.nanosecond
+            base1 += f"{self.nanosecond:03d}"
         else:
-            base1 += ".%.9d" % self.nanosecond
+            base1 += f".{self.nanosecond:09d}"
 
         return base1 + base2
 
diff --git a/pandas/_libs/tslibs/timezones.pyx b/pandas/_libs/tslibs/timezones.pyx
index bc1fdfae99de94..35ee87e714fa89 100644
--- a/pandas/_libs/tslibs/timezones.pyx
+++ b/pandas/_libs/tslibs/timezones.pyx
@@ -280,8 +280,8 @@ def infer_tzinfo(start, end):
     if start is not None and end is not None:
         tz = start.tzinfo
         if not tz_compare(tz, end.tzinfo):
-            msg = 'Inputs must both have the same timezone, {tz1} != {tz2}'
-            raise AssertionError(msg.format(tz1=tz, tz2=end.tzinfo))
+            raise AssertionError(f'Inputs must both have the same timezone, '
+                                 f'{tz} != {end.tzinfo}')
     elif start is not None:
         tz = start.tzinfo
     elif end is not None:
diff --git a/pandas/_libs/tslibs/tzconversion.pyx b/pandas/_libs/tslibs/tzconversion.pyx
index dd0c6fc75b06f3..b368f0fde3edcc 100644
--- a/pandas/_libs/tslibs/tzconversion.pyx
+++ b/pandas/_libs/tslibs/tzconversion.pyx
@@ -175,8 +175,8 @@ timedelta-like}
         if trans_idx.size == 1:
             stamp = _render_tstamp(vals[trans_idx])
             raise pytz.AmbiguousTimeError(
-                "Cannot infer dst time from %s as there "
-                "are no repeated times".format(stamp))
+                f"Cannot infer dst time from {stamp} as there "
+                f"are no repeated times")
         # Split the array into contiguous chunks (where the difference between
         # indices is 1).  These are effectively dst transitions in different
         # years which is useful for checking that there is not an ambiguous
@@ -200,8 +200,8 @@ timedelta-like}
                 switch_idx = (delta <= 0).nonzero()[0]
                 if switch_idx.size > 1:
                     raise pytz.AmbiguousTimeError(
-                        "There are %i dst switches when "
-                        "there should only be 1.".format(switch_idx.size))
+                        f"There are {switch_idx.size} dst switches when "
+                        f"there should only be 1.")
                 switch_idx = switch_idx[0] + 1
                 # Pull the only index and adjust
                 a_idx = grp[:switch_idx]
@@ -230,8 +230,8 @@ timedelta-like}
                 else:
                     stamp = _render_tstamp(val)
                     raise pytz.AmbiguousTimeError(
-                        "Cannot infer dst time from %r, try using the "
-                        "'ambiguous' argument".format(stamp))
+                        f"Cannot infer dst time from {stamp}, try using the "
+                        f"'ambiguous' argument")
         elif left != NPY_NAT:
             result[i] = left
         elif right != NPY_NAT:
@@ -246,8 +246,8 @@ timedelta-like}
                     # time
                     if -1 < shift_delta + remaining_mins < HOURS_NS:
                         raise ValueError(
-                            "The provided timedelta will relocalize on a "
-                            "nonexistent time: {}".format(nonexistent)
+                            f"The provided timedelta will relocalize on a "
+                            f"nonexistent time: {nonexistent}"
                         )
                     new_local = val + shift_delta
                 elif shift_forward: