diff --git a/pandas/_libs/algos_common_helper.pxi.in b/pandas/_libs/algos_common_helper.pxi.in
index 0d3f6664da9e3..97b7196da80bb 100644
--- a/pandas/_libs/algos_common_helper.pxi.in
+++ b/pandas/_libs/algos_common_helper.pxi.in
@@ -523,7 +523,7 @@ def put2d_{{name}}_{{dest_type}}(ndarray[{{c_type}}, ndim=2, cast=True] values,
         Py_ssize_t i, j, k
 
     k = len(values)
-    for j from 0 <= j < k:
+    for j in range(k):
         i = indexer[j]
         out[i] = values[j, loc]
 
diff --git a/pandas/_libs/algos_take_helper.pxi.in b/pandas/_libs/algos_take_helper.pxi.in
index 71bb1bb4fe9be..0e69324acd341 100644
--- a/pandas/_libs/algos_take_helper.pxi.in
+++ b/pandas/_libs/algos_take_helper.pxi.in
@@ -46,7 +46,7 @@ def get_dispatch(dtypes):
     fv = fill_value
 
     %(nogil_str)s
-    %(tab)sfor i from 0 <= i < n:
+    %(tab)sfor i in range(n):
     %(tab)s    idx = indexer[i]
     %(tab)s    if idx == -1:
     %(tab)s        out[i] = fv
@@ -74,10 +74,10 @@ def get_dispatch(dtypes):
             values.strides[1] == sizeof(%(c_type_out)s) and
             sizeof(%(c_type_out)s) * n >= 256):
 
-            for i from 0 <= i < n:
+            for i in range(n):
                 idx = indexer[i]
                 if idx == -1:
-                    for j from 0 <= j < k:
+                    for j in range(k):
                         out[i, j] = fv
                 else:
                     v = &values[idx, 0]
@@ -85,13 +85,13 @@ def get_dispatch(dtypes):
                     memmove(o, v, <size_t>(sizeof(%(c_type_out)s) * k))
             return
 
-    for i from 0 <= i < n:
+    for i in range(n):
         idx = indexer[i]
         if idx == -1:
-            for j from 0 <= j < k:
+            for j in range(k):
                 out[i, j] = fv
         else:
-            for j from 0 <= j < k:
+            for j in range(k):
                 out[i, j] = %(preval)svalues[idx, j]%(postval)s
 """
 
@@ -108,8 +108,8 @@ def get_dispatch(dtypes):
 
     fv = fill_value
 
-    for i from 0 <= i < n:
-        for j from 0 <= j < k:
+    for i in range(n):
+        for j in range(k):
             idx = indexer[j]
             if idx == -1:
                 out[i, j] = fv
@@ -246,13 +246,13 @@ def take_2d_multi_{{name}}_{{dest}}(ndarray[{{c_type_in}}, ndim=2] values,
     k = len(idx1)
 
     fv = fill_value
-    for i from 0 <= i < n:
+    for i in range(n):
         idx = idx0[i]
         if idx == -1:
-            for j from 0 <= j < k:
+            for j in range(k):
                 out[i, j] = fv
         else:
-            for j from 0 <= j < k:
+            for j in range(k):
                 if idx1[j] == -1:
                     out[i, j] = fv
                 else:
diff --git a/pandas/_libs/hashtable_func_helper.pxi.in b/pandas/_libs/hashtable_func_helper.pxi.in
index 521e564447c59..5aea0c65d6dd0 100644
--- a/pandas/_libs/hashtable_func_helper.pxi.in
+++ b/pandas/_libs/hashtable_func_helper.pxi.in
@@ -161,18 +161,18 @@ def duplicated_{{dtype}}({{scalar}}[:] values, object keep='first'):
         {{endif}}
     elif keep == 'first':
         {{if dtype == 'object'}}
-        for i from 0 <= i < n:
+        for i in range(n):
             kh_put_{{ttype}}(table, <PyObject*> values[i], &ret)
             out[i] = ret == 0
         {{else}}
         with nogil:
-            for i from 0 <= i < n:
+            for i in range(n):
                 kh_put_{{ttype}}(table, values[i], &ret)
                 out[i] = ret == 0
         {{endif}}
     else:
         {{if dtype == 'object'}}
-        for i from 0 <= i < n:
+        for i in range(n):
             value = values[i]
             k = kh_get_{{ttype}}(table, <PyObject*> value)
             if k != table.n_buckets:
@@ -185,7 +185,7 @@ def duplicated_{{dtype}}({{scalar}}[:] values, object keep='first'):
                 out[i] = 0
         {{else}}
         with nogil:
-            for i from 0 <= i < n:
+            for i in range(n):
                 value = values[i]
                 k = kh_get_{{ttype}}(table, value)
                 if k != table.n_buckets:
diff --git a/pandas/_libs/lib.pyx b/pandas/_libs/lib.pyx
index 89a96342a414b..e05905ab63624 100644
--- a/pandas/_libs/lib.pyx
+++ b/pandas/_libs/lib.pyx
@@ -78,29 +78,30 @@ cdef bint PY2 = sys.version_info[0] == 2
 cdef double nan = <double>np.NaN
 
 
-def values_from_object(object o):
+def values_from_object(object obj):
     """ return my values or the object if we are say an ndarray """
-    cdef f
+    cdef func  # TODO: Does declaring this without a type accomplish anything?
 
-    f = getattr(o, 'get_values', None)
-    if f is not None:
-        o = f()
+    func = getattr(obj, 'get_values', None)
+    if func is not None:
+        obj = func()
 
-    return o
+    return obj
 
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def memory_usage_of_objects(ndarray[object, ndim=1] arr):
+def memory_usage_of_objects(object[:] arr):
     """ return the memory usage of an object array in bytes,
     does not include the actual bytes of the pointers """
-    cdef Py_ssize_t i, n
-    cdef int64_t s = 0
+    cdef:
+        Py_ssize_t i, n
+        int64_t size = 0
 
     n = len(arr)
     for i in range(n):
-        s += arr[i].__sizeof__()
-    return s
+        size += arr[i].__sizeof__()
+    return size
 
 
 # ----------------------------------------------------------------------
diff --git a/pandas/_libs/ops.pyx b/pandas/_libs/ops.pyx
index ec9d8304f9243..a194f1588e231 100644
--- a/pandas/_libs/ops.pyx
+++ b/pandas/_libs/ops.pyx
@@ -1,5 +1,4 @@
 # -*- coding: utf-8 -*-
-# cython: profile=False
 import operator
 
 from cpython cimport (PyFloat_Check, PyBool_Check,
@@ -21,7 +20,7 @@ from missing cimport checknull
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def scalar_compare(ndarray[object] values, object val, object op):
+def scalar_compare(object[:] values, object val, object op):
     """
     Compare each element of `values` array with the scalar `val`, with
     the comparison operation described by `op`.
@@ -73,7 +72,7 @@ def scalar_compare(ndarray[object] values, object val, object op):
             else:
                 try:
                     result[i] = PyObject_RichCompareBool(x, val, flag)
-                except (TypeError):
+                except TypeError:
                     result[i] = True
     elif flag == Py_EQ:
         for i in range(n):
@@ -85,7 +84,7 @@ def scalar_compare(ndarray[object] values, object val, object op):
             else:
                 try:
                     result[i] = PyObject_RichCompareBool(x, val, flag)
-                except (TypeError):
+                except TypeError:
                     result[i] = False
 
     else:
@@ -103,7 +102,7 @@ def scalar_compare(ndarray[object] values, object val, object op):
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def vec_compare(ndarray[object] left, ndarray[object] right, object op):
+def vec_compare(object[:] left, object[:] right, object op):
     """
     Compare the elements of `left` with the elements of `right` pointwise,
     with the comparison operation described by `op`.
@@ -126,8 +125,8 @@ def vec_compare(ndarray[object] left, ndarray[object] right, object op):
         int flag
 
     if n != len(right):
-        raise ValueError('Arrays were different lengths: %d vs %d'
-                         % (n, len(right)))
+        raise ValueError('Arrays were different lengths: {n} vs {nright}'
+                         .format(n=n, nright=len(right)))
 
     if op is operator.lt:
         flag = Py_LT
@@ -170,7 +169,7 @@ def vec_compare(ndarray[object] left, ndarray[object] right, object op):
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def scalar_binop(ndarray[object] values, object val, object op):
+def scalar_binop(object[:] values, object val, object op):
     """
     Apply the given binary operator `op` between each element of the array
     `values` and the scalar `val`.
@@ -187,13 +186,13 @@ def scalar_binop(ndarray[object] values, object val, object op):
     """
     cdef:
         Py_ssize_t i, n = len(values)
-        ndarray[object] result
+        object[:] result
         object x
 
     result = np.empty(n, dtype=object)
     if val is None or is_nan(val):
-        result.fill(val)
-        return result
+        result[:] = val
+        return result.base  # `.base` to access underlying np.ndarray
 
     for i in range(n):
         x = values[i]
@@ -202,12 +201,12 @@ def scalar_binop(ndarray[object] values, object val, object op):
         else:
             result[i] = op(x, val)
 
-    return maybe_convert_bool(result)
+    return maybe_convert_bool(result.base)
 
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def vec_binop(ndarray[object] left, ndarray[object] right, object op):
+def vec_binop(object[:] left, object[:] right, object op):
     """
     Apply the given binary operator `op` pointwise to the elements of
     arrays `left` and `right`.
@@ -224,11 +223,11 @@ def vec_binop(ndarray[object] left, ndarray[object] right, object op):
     """
     cdef:
         Py_ssize_t i, n = len(left)
-        ndarray[object] result
+        object[:] result
 
     if n != len(right):
-        raise ValueError('Arrays were different lengths: %d vs %d'
-                         % (n, len(right)))
+        raise ValueError('Arrays were different lengths: {n} vs {nright}'
+                         .format(n=n, nright=len(right)))
 
     result = np.empty(n, dtype=object)
 
@@ -245,7 +244,7 @@ def vec_binop(ndarray[object] left, ndarray[object] right, object op):
             else:
                 raise
 
-    return maybe_convert_bool(result)
+    return maybe_convert_bool(result.base)  # `.base` to access np.ndarray
 
 
 def maybe_convert_bool(ndarray[object] arr,
@@ -270,7 +269,7 @@ def maybe_convert_bool(ndarray[object] arr,
     if false_values is not None:
         false_vals = false_vals | set(false_values)
 
-    for i from 0 <= i < n:
+    for i in range(n):
         val = arr[i]
 
         if PyBool_Check(val):
diff --git a/pandas/_libs/sparse.pyx b/pandas/_libs/sparse.pyx
index 2abd270652433..7f5990ce5d65c 100644
--- a/pandas/_libs/sparse.pyx
+++ b/pandas/_libs/sparse.pyx
@@ -148,7 +148,7 @@ cdef class IntIndex(SparseIndex):
         new_indices = np.empty(min(
             len(xindices), len(yindices)), dtype=np.int32)
 
-        for xi from 0 <= xi < self.npoints:
+        for xi in range(self.npoints):
             xind = xindices[xi]
 
             while yi < y.npoints and yindices[yi] < xind:
@@ -292,7 +292,7 @@ cpdef get_blocks(ndarray[int32_t, ndim=1] indices):
 
     # TODO: two-pass algorithm faster?
     prev = block = indices[0]
-    for i from 1 <= i < npoints:
+    for i in range(1, npoints):
         cur = indices[i]
         if cur - prev > 1:
             # new block
@@ -383,21 +383,22 @@ cdef class BlockIndex(SparseIndex):
         if len(blocs) != len(blengths):
             raise ValueError('block bound arrays must be same length')
 
-        for i from 0 <= i < self.nblocks:
+        for i in range(self.nblocks):
             if i > 0:
                 if blocs[i] <= blocs[i - 1]:
                     raise ValueError('Locations not in ascending order')
 
             if i < self.nblocks - 1:
                 if blocs[i] + blengths[i] > blocs[i + 1]:
-                    raise ValueError('Block %d overlaps' % i)
+                    raise ValueError('Block {idx} overlaps'.format(idx=i))
             else:
                 if blocs[i] + blengths[i] > self.length:
-                    raise ValueError('Block %d extends beyond end' % i)
+                    raise ValueError('Block {idx} extends beyond end'
+                                     .format(idx=i))
 
             # no zero-length blocks
             if blengths[i] == 0:
-                raise ValueError('Zero-length block %d' % i)
+                raise ValueError('Zero-length block {idx}'.format(idx=i))
 
     def equals(self, other):
         if not isinstance(other, BlockIndex):
@@ -422,10 +423,10 @@ cdef class BlockIndex(SparseIndex):
 
         indices = np.empty(self.npoints, dtype=np.int32)
 
-        for b from 0 <= b < self.nblocks:
+        for b in range(self.nblocks):
             offset = self.locbuf[b]
 
-            for j from 0 <= j < self.lenbuf[b]:
+            for j in range(self.lenbuf[b]):
                 indices[i] = offset + j
                 i += 1
 
@@ -551,7 +552,7 @@ cdef class BlockIndex(SparseIndex):
             return -1
 
         cum_len = 0
-        for i from 0 <= i < self.nblocks:
+        for i in range(self.nblocks):
             if index >= locs[i] and index < locs[i] + lens[i]:
                 return cum_len + index - locs[i]
             cum_len += lens[i]
@@ -579,11 +580,11 @@ cdef class BlockIndex(SparseIndex):
         if self.npoints == 0:
             return results
 
-        for i from 0 <= i < n:
+        for i in range(n):
             ind_val = indexer[i]
             if not (ind_val < 0 or self.length <= ind_val):
                 cum_len = 0
-                for j from 0 <= j < self.nblocks:
+                for j in range(self.nblocks):
                     if ind_val >= locs[j] and ind_val < locs[j] + lens[j]:
                         results[i] = cum_len + ind_val - locs[j]
                     cum_len += lens[j]
@@ -824,7 +825,7 @@ def get_reindexer(ndarray[object, ndim=1] values, dict index_map):
 
 #     out = np.empty(length, dtype=np.float64)
 
-#     for i from 0 <= i < length:
+#     for i in range(length):
 #         if indexer[i] == -1:
 #             pass
 
diff --git a/pandas/_libs/sparse_op_helper.pxi.in b/pandas/_libs/sparse_op_helper.pxi.in
index d1d9a6f02a72c..2843a3cf7dd28 100644
--- a/pandas/_libs/sparse_op_helper.pxi.in
+++ b/pandas/_libs/sparse_op_helper.pxi.in
@@ -190,7 +190,7 @@ cdef inline tuple block_op_{{opname}}_{{dtype}}(ndarray x_,
     # Wow, what a hack job. Need to do something about this
 
     # walk the two SparseVectors, adding matched locations...
-    for out_i from 0 <= out_i < out_index.npoints:
+    for out_i in range(out_index.npoints):
         if yblock == yindex.nblocks:
             # use y fill value
             out[out_i] = {{(opname, 'x[xi]', 'yfill', dtype) | get_op}}
@@ -286,7 +286,7 @@ cdef inline tuple int_op_{{opname}}_{{dtype}}(ndarray x_, IntIndex xindex,
     out_indices = out_index.indices
 
     # walk the two SparseVectors, adding matched locations...
-    for out_i from 0 <= out_i < out_index.npoints:
+    for out_i in range(out_index.npoints):
         if xi == xindex.npoints:
             # use x fill value
             out[out_i] = {{(opname, 'xfill', 'y[yi]', dtype) | get_op}}
diff --git a/pandas/_libs/src/compat_helper.h b/pandas/_libs/src/compat_helper.h
index 116cd91070a60..462f53392adee 100644
--- a/pandas/_libs/src/compat_helper.h
+++ b/pandas/_libs/src/compat_helper.h
@@ -11,7 +11,7 @@ The full license is in the LICENSE file, distributed with this software.
 #define PANDAS__LIBS_SRC_COMPAT_HELPER_H_
 
 #include "Python.h"
-#include "helper.h"
+#include "inline_helper.h"
 
 /*
 PySlice_GetIndicesEx changes signature in PY3
diff --git a/pandas/_libs/src/helper.h b/pandas/_libs/src/inline_helper.h
similarity index 80%
rename from pandas/_libs/src/helper.h
rename to pandas/_libs/src/inline_helper.h
index 26b4d033b963b..397ec8e7b2cb8 100644
--- a/pandas/_libs/src/helper.h
+++ b/pandas/_libs/src/inline_helper.h
@@ -7,8 +7,8 @@ Distributed under the terms of the BSD Simplified License.
 The full license is in the LICENSE file, distributed with this software.
 */
 
-#ifndef PANDAS__LIBS_SRC_HELPER_H_
-#define PANDAS__LIBS_SRC_HELPER_H_
+#ifndef PANDAS__LIBS_SRC_INLINE_HELPER_H_
+#define PANDAS__LIBS_SRC_INLINE_HELPER_H_
 
 #ifndef PANDAS_INLINE
   #if defined(__GNUC__)
@@ -22,4 +22,4 @@ The full license is in the LICENSE file, distributed with this software.
   #endif
 #endif
 
-#endif  // PANDAS__LIBS_SRC_HELPER_H_
+#endif  // PANDAS__LIBS_SRC_INLINE_HELPER_H_
diff --git a/pandas/_libs/src/klib/khash.h b/pandas/_libs/src/klib/khash.h
index 869607a44c001..77ec519cc24da 100644
--- a/pandas/_libs/src/klib/khash.h
+++ b/pandas/_libs/src/klib/khash.h
@@ -112,6 +112,7 @@ int main() {
 #include <stdlib.h>
 #include <string.h>
 #include <limits.h>
+#include "../inline_helper.h"
 
 
 #if UINT_MAX == 0xffffffffu
@@ -130,18 +131,6 @@ typedef signed long long khint64_t;
 
 typedef double khfloat64_t;
 
-#ifndef PANDAS_INLINE
-  #if defined(__GNUC__)
-    #define PANDAS_INLINE static __inline__
-  #elif defined(_MSC_VER)
-    #define PANDAS_INLINE static __inline
-  #elif defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
-    #define PANDAS_INLINE static inline
-  #else
-    #define PANDAS_INLINE
-  #endif
-#endif
-
 typedef khint32_t khint_t;
 typedef khint_t khiter_t;
 
diff --git a/pandas/_libs/src/numpy_helper.h b/pandas/_libs/src/numpy_helper.h
index 753cba6ce62aa..d44334906901a 100644
--- a/pandas/_libs/src/numpy_helper.h
+++ b/pandas/_libs/src/numpy_helper.h
@@ -11,7 +11,7 @@ The full license is in the LICENSE file, distributed with this software.
 #define PANDAS__LIBS_SRC_NUMPY_HELPER_H_
 
 #include "Python.h"
-#include "helper.h"
+#include "inline_helper.h"
 #include "numpy/arrayobject.h"
 #include "numpy/arrayscalars.h"
 
diff --git a/pandas/_libs/src/parse_helper.h b/pandas/_libs/src/parse_helper.h
index d17d9166ea3ee..4f9f825b15ffe 100644
--- a/pandas/_libs/src/parse_helper.h
+++ b/pandas/_libs/src/parse_helper.h
@@ -12,7 +12,7 @@ The full license is in the LICENSE file, distributed with this software.
 
 #include <errno.h>
 #include <float.h>
-#include "helper.h"
+#include "inline_helper.h"
 #include "headers/portable.h"
 
 static double xstrtod(const char *p, char **q, char decimal, char sci,
diff --git a/pandas/_libs/src/parser/tokenizer.c b/pandas/_libs/src/parser/tokenizer.c
index a18d12616a802..da0a9f7498aa8 100644
--- a/pandas/_libs/src/parser/tokenizer.c
+++ b/pandas/_libs/src/parser/tokenizer.c
@@ -363,7 +363,7 @@ static int push_char(parser_t *self, char c) {
     return 0;
 }
 
-int P_INLINE end_field(parser_t *self) {
+int PANDAS_INLINE end_field(parser_t *self) {
     // XXX cruft
     if (self->words_len >= self->words_cap) {
         TRACE(
@@ -1381,11 +1381,11 @@ int tokenize_all_rows(parser_t *self) {
     return status;
 }
 
-P_INLINE void uppercase(char *p) {
+PANDAS_INLINE void uppercase(char *p) {
     for (; *p; ++p) *p = toupper(*p);
 }
 
-int P_INLINE to_longlong(char *item, long long *p_value) {
+int PANDAS_INLINE to_longlong(char *item, long long *p_value) {
     char *p_end;
 
     // Try integer conversion.  We explicitly give the base to be 10. If
diff --git a/pandas/_libs/src/parser/tokenizer.h b/pandas/_libs/src/parser/tokenizer.h
index 63baf91e3c136..9fc3593aaaf5b 100644
--- a/pandas/_libs/src/parser/tokenizer.h
+++ b/pandas/_libs/src/parser/tokenizer.h
@@ -27,6 +27,7 @@ See LICENSE for the license
 #define ERROR_INVALID_CHARS 3
 
 #include "../headers/stdint.h"
+#include "../inline_helper.h"
 
 #include "khash.h"
 
@@ -38,17 +39,6 @@ See LICENSE for the license
 #define REACHED_EOF 1
 #define CALLING_READ_FAILED 2
 
-#ifndef P_INLINE
-#if defined(__GNUC__)
-#define P_INLINE static __inline__
-#elif defined(_MSC_VER)
-#define P_INLINE
-#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
-#define P_INLINE static inline
-#else
-#define P_INLINE
-#endif
-#endif
 
 #if defined(_MSC_VER)
 #define strtoll _strtoi64
diff --git a/pandas/_libs/src/skiplist.h b/pandas/_libs/src/skiplist.h
index f9527e72f577e..60c1a56727777 100644
--- a/pandas/_libs/src/skiplist.h
+++ b/pandas/_libs/src/skiplist.h
@@ -20,18 +20,7 @@ Python recipe (http://rhettinger.wordpress.com/2010/02/06/lost-knowledge/)
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-
-#ifndef PANDAS_INLINE
-#if defined(__GNUC__)
-#define PANDAS_INLINE static __inline__
-#elif defined(_MSC_VER)
-#define PANDAS_INLINE static __inline
-#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
-#define PANDAS_INLINE static inline
-#else
-#define PANDAS_INLINE
-#endif
-#endif
+#include "inline_helper.h"
 
 PANDAS_INLINE float __skiplist_nanf(void) {
     const union {
diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index 7e9e8b720872d..70a3f3f410636 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -1,5 +1,4 @@
 # -*- coding: utf-8 -*-
-# cython: profile=False
 import re
 
 cimport numpy as cnp
diff --git a/pandas/_libs/tslibs/np_datetime.pxd b/pandas/_libs/tslibs/np_datetime.pxd
index a585259286a58..c3d229d4e5006 100644
--- a/pandas/_libs/tslibs/np_datetime.pxd
+++ b/pandas/_libs/tslibs/np_datetime.pxd
@@ -46,7 +46,7 @@ cdef extern from "numpy/ndarraytypes.h":
         NPY_FR_fs
         NPY_FR_as
 
-cdef extern from "../src/datetime/np_datetime.h":
+cdef extern from "src/datetime/np_datetime.h":
     ctypedef struct pandas_timedeltastruct:
         int64_t days
         int32_t hrs, min, sec, ms, us, ns, seconds, microseconds, nanoseconds
diff --git a/pandas/_libs/tslibs/np_datetime.pyx b/pandas/_libs/tslibs/np_datetime.pyx
index 76838c7a23b24..a0099837e876a 100644
--- a/pandas/_libs/tslibs/np_datetime.pyx
+++ b/pandas/_libs/tslibs/np_datetime.pyx
@@ -15,7 +15,7 @@ PyDateTime_IMPORT
 
 from numpy cimport int64_t
 
-cdef extern from "../src/datetime/np_datetime.h":
+cdef extern from "src/datetime/np_datetime.h":
     int cmp_npy_datetimestruct(npy_datetimestruct *a,
                                npy_datetimestruct *b)
 
@@ -33,7 +33,7 @@ cdef extern from "../src/datetime/np_datetime.h":
 
     npy_datetimestruct _NS_MIN_DTS, _NS_MAX_DTS
 
-cdef extern from "../src/datetime/np_datetime_strings.h":
+cdef extern from "src/datetime/np_datetime_strings.h":
     int parse_iso_8601_datetime(char *str, int len,
                                 npy_datetimestruct *out,
                                 int *out_local, int *out_tzoffset)
diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 7a279a41709ec..8c53fabffdbeb 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1,5 +1,4 @@
 # -*- coding: utf-8 -*-
-# cython: profile=False
 
 cimport cython
 from cython cimport Py_ssize_t
@@ -31,17 +30,6 @@ from np_datetime cimport (npy_datetimestruct,
 # Constants
 
 
-class WeekDay(object):
-    # TODO: Remove: This is not used outside of tests
-    MON = 0
-    TUE = 1
-    WED = 2
-    THU = 3
-    FRI = 4
-    SAT = 5
-    SUN = 6
-
-
 _offset_to_period_map = {
     'WEEKDAY': 'D',
     'EOM': 'M',
diff --git a/pandas/_libs/tslibs/parsing.pyx b/pandas/_libs/tslibs/parsing.pyx
index 61fb48c6913d3..6ee6c4b9d9026 100644
--- a/pandas/_libs/tslibs/parsing.pyx
+++ b/pandas/_libs/tslibs/parsing.pyx
@@ -1,25 +1,22 @@
 # -*- coding: utf-8 -*-
-# cython: profile=False
 """
 Parsing functions for datetime and datetime-like strings.
 """
 import sys
 import re
+import time
 
-from cython cimport Py_ssize_t
-
+from cython import Py_ssize_t
 
 from cpython.datetime cimport datetime
-import time
+
 
 import numpy as np
 
 # Avoid import from outside _libs
 if sys.version_info.major == 2:
-    string_types = basestring
     from StringIO import StringIO
 else:
-    string_types = str
     from io import StringIO
 
 
@@ -113,7 +110,9 @@ def parse_time_string(arg, freq=None, dayfirst=None, yearfirst=None):
     -------
     datetime, datetime/dateutil.parser._result, str
     """
-    if not isinstance(arg, string_types):
+    if not isinstance(arg, (str, unicode)):
+        # Note: cython recognizes `unicode` in both py2/py3, optimizes
+        # this check into a C call.
         return arg
 
     if getattr(freq, "_typ", None) == "dateoffset":
@@ -132,15 +131,22 @@ def parse_time_string(arg, freq=None, dayfirst=None, yearfirst=None):
     return res
 
 
-def parse_datetime_string_with_reso(date_string, freq=None, dayfirst=False,
-                                    yearfirst=False, **kwargs):
+cdef parse_datetime_string_with_reso(date_string, freq=None, dayfirst=False,
+                                     yearfirst=False):
     """parse datetime string, only returns datetime
 
     Returns
     -------
-    datetime
+    parsed : datetime
+    parsed2 : datetime/dateutil.parser._result
+    reso : str
+        inferred resolution
+
+    Raises
+    ------
+    ValueError : preliminary check suggests string is not datetime
+    DateParseError : error within dateutil
     """
-
     cdef:
         object parsed, reso
 
@@ -156,12 +162,13 @@ def parse_datetime_string_with_reso(date_string, freq=None, dayfirst=False,
 
     try:
         parsed, reso = dateutil_parse(date_string, _DEFAULT_DATETIME,
-                                      dayfirst=dayfirst, yearfirst=yearfirst)
+                                      dayfirst=dayfirst, yearfirst=yearfirst,
+                                      ignoretz=False, tzinfos=None)
     except Exception as e:
         # TODO: allow raise of errors within instead
         raise DateParseError(e)
     if parsed is None:
-        raise DateParseError("Could not parse %s" % date_string)
+        raise DateParseError("Could not parse {dstr}".format(dstr=date_string))
     return parsed, parsed, reso
 
 
@@ -190,7 +197,7 @@ cdef inline object _parse_dateabbr_string(object date_string, object default,
         int year, quarter = -1, month, mnum, date_len
 
     # special handling for possibilities eg, 2Q2005, 2Q05, 2005Q1, 05Q1
-    assert isinstance(date_string, string_types)
+    assert isinstance(date_string, (str, unicode))
 
     # len(date_string) == 0
     # should be NaT???
@@ -243,8 +250,8 @@ cdef inline object _parse_dateabbr_string(object date_string, object default,
 
             if not (1 <= quarter <= 4):
                 msg = ('Incorrect quarterly string is given, quarter must be '
-                       'between 1 and 4: {0}')
-                raise DateParseError(msg.format(date_string))
+                       'between 1 and 4: {dstr}')
+                raise DateParseError(msg.format(dstr=date_string))
 
             if freq is not None:
                 # hack attack, #1228
@@ -252,7 +259,7 @@ cdef inline object _parse_dateabbr_string(object date_string, object default,
                     mnum = MONTH_NUMBERS[_get_rule_month(freq)] + 1
                 except (KeyError, ValueError):
                     msg = ('Unable to retrieve month information from given '
-                           'freq: {0}').format(freq)
+                           'freq: {freq}'.format(freq=freq))
                     raise DateParseError(msg)
 
                 month = (mnum + (quarter - 1) * 3) % 12 + 1
@@ -289,8 +296,8 @@ cdef inline object _parse_dateabbr_string(object date_string, object default,
     raise ValueError('Unable to parse {0}'.format(date_string))
 
 
-def dateutil_parse(object timestr, object default, ignoretz=False,
-                   tzinfos=None, **kwargs):
+cdef dateutil_parse(object timestr, object default, ignoretz=False,
+                    tzinfos=None, dayfirst=None, yearfirst=None):
     """ lifted from dateutil to get resolution"""
 
     cdef:
@@ -299,15 +306,15 @@ def dateutil_parse(object timestr, object default, ignoretz=False,
         dict repl = {}
 
     fobj = StringIO(str(timestr))
-    res = DEFAULTPARSER._parse(fobj, **kwargs)
+    res = DEFAULTPARSER._parse(fobj, dayfirst=dayfirst, yearfirst=yearfirst)
 
     # dateutil 2.2 compat
     if isinstance(res, tuple):  # PyTuple_Check
         res, _ = res
 
     if res is None:
-        msg = "Unknown datetime string format, unable to parse: {0}"
-        raise ValueError(msg.format(timestr))
+        msg = "Unknown datetime string format, unable to parse: {timestr}"
+        raise ValueError(msg.format(timestr=timestr))
 
     for attr in ["year", "month", "day", "hour",
                  "minute", "second", "microsecond"]:
@@ -317,8 +324,8 @@ def dateutil_parse(object timestr, object default, ignoretz=False,
             reso = attr
 
     if reso is None:
-        msg = "Unable to parse datetime string: {0}"
-        raise ValueError(msg.format(timestr))
+        msg = "Unable to parse datetime string: {timestr}"
+        raise ValueError(msg.format(timestr=timestr))
 
     if reso == 'microsecond':
         if repl['microsecond'] == 0:
@@ -337,7 +344,7 @@ def dateutil_parse(object timestr, object default, ignoretz=False,
                 tzdata = tzinfos.get(res.tzname)
             if isinstance(tzdata, datetime.tzinfo):
                 tzinfo = tzdata
-            elif isinstance(tzdata, string_types):
+            elif isinstance(tzdata, (str, unicode)):
                 tzinfo = _dateutil_tzstr(tzdata)
             elif isinstance(tzdata, int):
                 tzinfo = tzoffset(res.tzname, tzdata)
@@ -575,7 +582,7 @@ def _guess_datetime_format(dt_str, dayfirst=False, dt_str_parse=du_parse,
     if dt_str_parse is None or dt_str_split is None:
         return None
 
-    if not isinstance(dt_str, string_types):
+    if not isinstance(dt_str, (str, unicode)):
         return None
 
     day_attribute_and_format = (('day',), '%d', 2)
diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
index 65b37759ce9ce..f68b6d8fdef57 100644
--- a/pandas/_libs/tslibs/period.pyx
+++ b/pandas/_libs/tslibs/period.pyx
@@ -26,12 +26,12 @@ from np_datetime cimport (npy_datetimestruct, dtstruct_to_dt64,
                           pandas_datetime_to_datetimestruct,
                           NPY_DATETIMEUNIT, NPY_FR_D)
 
-cdef extern from "../src/datetime/np_datetime.h":
+cdef extern from "src/datetime/np_datetime.h":
     int64_t npy_datetimestruct_to_datetime(NPY_DATETIMEUNIT fr,
                                            npy_datetimestruct *d) nogil
 
 cimport util
-from util cimport is_period_object, is_string_object, INT32_MIN
+from util cimport is_period_object, is_string_object
 
 from timestamps import Timestamp
 from timezones cimport is_utc, is_tzlocal, get_dst_info
@@ -53,6 +53,8 @@ from offsets cimport to_offset
 from offsets import _Tick
 
 cdef bint PY2 = str == bytes
+cdef enum:
+    INT32_MIN = -2147483648
 
 
 ctypedef struct asfreq_info:
@@ -67,60 +69,24 @@ ctypedef int64_t (*freq_conv_func)(int64_t, asfreq_info*) nogil
 cdef extern from *:
     """
     /*** FREQUENCY CONSTANTS ***/
+    // See frequencies.pyx for more detailed variants
 
     #define FR_ANN 1000      /* Annual */
-    #define FR_ANNDEC FR_ANN /* Annual - December year end*/
-    #define FR_ANNJAN 1001   /* Annual - January year end*/
-    #define FR_ANNFEB 1002   /* Annual - February year end*/
-    #define FR_ANNMAR 1003   /* Annual - March year end*/
-    #define FR_ANNAPR 1004   /* Annual - April year end*/
-    #define FR_ANNMAY 1005   /* Annual - May year end*/
-    #define FR_ANNJUN 1006   /* Annual - June year end*/
-    #define FR_ANNJUL 1007   /* Annual - July year end*/
-    #define FR_ANNAUG 1008   /* Annual - August year end*/
-    #define FR_ANNSEP 1009   /* Annual - September year end*/
-    #define FR_ANNOCT 1010   /* Annual - October year end*/
-    #define FR_ANNNOV 1011   /* Annual - November year end*/
-
-    /* The standard quarterly frequencies with various fiscal year ends
-       eg, Q42005 for Q@OCT runs Aug 1, 2005 to Oct 31, 2005 */
     #define FR_QTR 2000      /* Quarterly - December year end (default Q) */
-    #define FR_QTRDEC FR_QTR /* Quarterly - December year end */
-    #define FR_QTRJAN 2001   /* Quarterly - January year end */
-    #define FR_QTRFEB 2002   /* Quarterly - February year end */
-    #define FR_QTRMAR 2003   /* Quarterly - March year end */
-    #define FR_QTRAPR 2004   /* Quarterly - April year end */
-    #define FR_QTRMAY 2005   /* Quarterly - May year end */
-    #define FR_QTRJUN 2006   /* Quarterly - June year end */
-    #define FR_QTRJUL 2007   /* Quarterly - July year end */
-    #define FR_QTRAUG 2008   /* Quarterly - August year end */
-    #define FR_QTRSEP 2009   /* Quarterly - September year end */
-    #define FR_QTROCT 2010   /* Quarterly - October year end */
-    #define FR_QTRNOV 2011   /* Quarterly - November year end */
-
-    #define FR_MTH 3000 /* Monthly */
-
-    #define FR_WK 4000     /* Weekly */
-    #define FR_WKSUN FR_WK /* Weekly - Sunday end of week */
-    #define FR_WKMON 4001  /* Weekly - Monday end of week */
-    #define FR_WKTUE 4002  /* Weekly - Tuesday end of week */
-    #define FR_WKWED 4003  /* Weekly - Wednesday end of week */
-    #define FR_WKTHU 4004  /* Weekly - Thursday end of week */
-    #define FR_WKFRI 4005  /* Weekly - Friday end of week */
-    #define FR_WKSAT 4006  /* Weekly - Saturday end of week */
-
-    #define FR_BUS 5000 /* Business days */
-    #define FR_DAY 6000 /* Daily */
-    #define FR_HR 7000  /* Hourly */
-    #define FR_MIN 8000 /* Minutely */
-    #define FR_SEC 9000 /* Secondly */
-    #define FR_MS 10000 /* Millisecondly */
-    #define FR_US 11000 /* Microsecondly */
-    #define FR_NS 12000 /* Nanosecondly */
-
-    #define FR_UND -10000 /* Undefined */
-
-    static int64_t daytime_conversion_factor_matrix[7][7] = {
+    #define FR_MTH 3000      /* Monthly */
+    #define FR_WK 4000       /* Weekly */
+    #define FR_BUS 5000      /* Business days */
+    #define FR_DAY 6000      /* Daily */
+    #define FR_HR 7000       /* Hourly */
+    #define FR_MIN 8000      /* Minutely */
+    #define FR_SEC 9000      /* Secondly */
+    #define FR_MS 10000      /* Millisecondly */
+    #define FR_US 11000      /* Microsecondly */
+    #define FR_NS 12000      /* Nanosecondly */
+    #define FR_UND -10000    /* Undefined */
+
+    // must use npy typedef b/c int64_t is aliased in cython-generated c
+    static npy_int64 daytime_conversion_factor_matrix[7][7] = {
         {1, 24, 1440, 86400, 86400000, 86400000000, 86400000000000},
         {0,  1,   60,  3600,  3600000,  3600000000,  3600000000000},
         {0,  0,   1,     60,    60000,    60000000,    60000000000},
@@ -128,26 +94,9 @@ cdef extern from *:
         {0,  0,   0,      0,        1,        1000,        1000000},
         {0,  0,   0,      0,        0,           1,           1000},
         {0,  0,   0,      0,        0,           0,              1}};
-
-    int max_value(int a, int b) { return a > b ? a : b; }
-
-    static int min_value(int a, int b) { return a < b ? a : b; }
-
-    npy_int64 get_daytime_conversion_factor(int from_index, int to_index) {
-        int row = min_value(from_index, to_index);
-        int col = max_value(from_index, to_index);
-        // row or col < 6 means frequency strictly lower than Daily, which
-        // do not use daytime_conversion_factors
-        if (row < 6) {
-            return 0;
-        } else if (col < 6) {
-            return 0;
-        }
-        return daytime_conversion_factor_matrix[row - 6][col - 6];
-    }
     """
-    int64_t get_daytime_conversion_factor(int from_index, int to_index) nogil
-    int max_value(int left, int right) nogil
+    int64_t daytime_conversion_factor_matrix[7][7]
+    # TODO: Can we get these frequencies from frequencies.FreqGroup?
     int FR_ANN
     int FR_QTR
     int FR_MTH
@@ -163,6 +112,31 @@ cdef extern from *:
     int FR_UND
 
 
+cdef int max_value(int left, int right) nogil:
+    if left > right:
+        return left
+    return right
+
+
+cdef int min_value(int left, int right) nogil:
+    if left < right:
+        return left
+    return right
+
+
+cdef int64_t get_daytime_conversion_factor(int from_index, int to_index) nogil:
+    cdef:
+        int row = min_value(from_index, to_index)
+        int col = max_value(from_index, to_index)
+    # row or col < 6 means frequency strictly lower than Daily, which
+    # do not use daytime_conversion_factors
+    if row < 6:
+        return 0
+    elif col < 6:
+        return 0
+    return daytime_conversion_factor_matrix[row - 6][col - 6]
+
+
 cdef int64_t nofunc(int64_t ordinal, asfreq_info *af_info):
     return np.iinfo(np.int32).min
 
@@ -1250,7 +1224,7 @@ 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: %d' % freq)
+            raise ValueError('Unknown freq: {freq}'.format(freq=freq))
 
     return _period_strftime(value, freq, fmt)
 
@@ -1415,7 +1389,7 @@ 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: %d' % code)
+        raise ValueError('Unrecognized period code: {code}'.format(code=code))
 
     sz = len(arr)
     out = np.empty(sz, dtype=np.int64)
@@ -1597,7 +1571,8 @@ cdef class _Period(object):
 
         if freq.n <= 0:
             raise ValueError('Frequency must be positive, because it'
-                             ' represents span: {0}'.format(freq.freqstr))
+                             ' represents span: {freqstr}'
+                             .format(freqstr=freq.freqstr))
 
         return freq
 
@@ -1629,8 +1604,9 @@ cdef class _Period(object):
                 return NotImplemented
             elif op == Py_NE:
                 return NotImplemented
-            raise TypeError('Cannot compare type %r with type %r' %
-                            (type(self).__name__, type(other).__name__))
+            raise TypeError('Cannot compare type {cls} with type {typ}'
+                            .format(cls=type(self).__name__,
+                                    typ=type(other).__name__))
 
     def __hash__(self):
         return hash((self.ordinal, self.freqstr))
@@ -2428,8 +2404,8 @@ class Period(_Period):
             freq = cls._maybe_convert_freq(freq)
 
         if ordinal is not None and value is not None:
-            raise ValueError(("Only value or ordinal but not both should be "
-                              "given but not both"))
+            raise ValueError("Only value or ordinal but not both should be "
+                             "given but not both")
         elif ordinal is not None:
             if not util.is_integer_object(ordinal):
                 raise ValueError("Ordinal must be an integer")
@@ -2481,7 +2457,8 @@ class Period(_Period):
                     freq = Resolution.get_freq(reso)
                 except KeyError:
                     raise ValueError(
-                        "Invalid frequency or could not infer: %s" % reso)
+                        "Invalid frequency or could not infer: {reso}"
+                        .format(reso=reso))
 
         elif isinstance(value, datetime):
             dt = value
diff --git a/pandas/_libs/tslibs/resolution.pyx b/pandas/_libs/tslibs/resolution.pyx
index 83be739a6ae0a..4e3350395400c 100644
--- a/pandas/_libs/tslibs/resolution.pyx
+++ b/pandas/_libs/tslibs/resolution.pyx
@@ -1,5 +1,4 @@
 # -*- coding: utf-8 -*-
-# cython: profile=False
 
 from cython cimport Py_ssize_t
 
diff --git a/pandas/_libs/tslibs/src/datetime/np_datetime.c b/pandas/_libs/tslibs/src/datetime/np_datetime.c
index 659afd152106d..866c9ca9d3ac7 100644
--- a/pandas/_libs/tslibs/src/datetime/np_datetime.c
+++ b/pandas/_libs/tslibs/src/datetime/np_datetime.c
@@ -50,18 +50,6 @@ int is_leapyear(npy_int64 year) {
            ((year % 100) != 0 || (year % 400) == 0);
 }
 
-/*
- * Sakamoto's method, from wikipedia
- */
-int dayofweek(int y, int m, int d) {
-    int day;
-    static const int t[] = {0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4};
-    y -= m < 3;
-    day = (y + y / 4 - y / 100 + y / 400 + t[m - 1] + d) % 7;
-    // convert to python day
-    return (day + 6) % 7;
-}
-
 /*
  * Adjusts a datetimestruct based on a minutes offset. Assumes
  * the current values are valid.g
diff --git a/pandas/_libs/tslibs/src/datetime/np_datetime.h b/pandas/_libs/tslibs/src/datetime/np_datetime.h
index 3974d5083f51b..549d38409ca83 100644
--- a/pandas/_libs/tslibs/src/datetime/np_datetime.h
+++ b/pandas/_libs/tslibs/src/datetime/np_datetime.h
@@ -48,8 +48,6 @@ void pandas_timedelta_to_timedeltastruct(npy_timedelta val,
                                          NPY_DATETIMEUNIT fr,
                                          pandas_timedeltastruct *result);
 
-int dayofweek(int y, int m, int d);
-
 extern const int days_per_month_table[2][12];
 
 // stuff numpy-derived code needs in header
diff --git a/pandas/_libs/tslibs/strptime.pyx b/pandas/_libs/tslibs/strptime.pyx
index 8e7c55051a3c0..d472320cfdb12 100644
--- a/pandas/_libs/tslibs/strptime.pyx
+++ b/pandas/_libs/tslibs/strptime.pyx
@@ -1,11 +1,11 @@
 # -*- coding: utf-8 -*-
-# cython: profile=False
 """Strptime-related classes and functions.
 """
 import time
 import locale
 import calendar
 import re
+from datetime import date as datetime_date
 
 
 # Python 2 vs Python 3
@@ -20,14 +20,14 @@ except:
         except:
             from _dummy_thread import allocate_lock as _thread_allocate_lock
 
-import pytz
-
 from cython cimport Py_ssize_t
 
+
+import pytz
+
 import numpy as np
 from numpy cimport int64_t
 
-from datetime import date as datetime_date
 
 from np_datetime cimport (check_dts_bounds,
                           dtstruct_to_dt64, npy_datetimestruct)
diff --git a/pandas/_libs/tslibs/timedeltas.pxd b/pandas/_libs/tslibs/timedeltas.pxd
index 2413c281e0a52..ef9fd3207e5f0 100644
--- a/pandas/_libs/tslibs/timedeltas.pxd
+++ b/pandas/_libs/tslibs/timedeltas.pxd
@@ -1,8 +1,6 @@
 # -*- coding: utf-8 -*-
 # cython: profile=False
 
-from cpython.datetime cimport timedelta
-
 from numpy cimport int64_t
 
 # Exposed for tslib, not intended for outside use.
diff --git a/pandas/_libs/tslibs/timestamps.pyx b/pandas/_libs/tslibs/timestamps.pyx
index eb5c0076a868a..67420fda8aa51 100644
--- a/pandas/_libs/tslibs/timestamps.pyx
+++ b/pandas/_libs/tslibs/timestamps.pyx
@@ -17,8 +17,7 @@ from cpython.datetime cimport (datetime,
 PyDateTime_IMPORT
 
 from util cimport (is_datetime64_object, is_timedelta64_object,
-                   is_integer_object, is_string_object, is_array,
-                   INT64_MAX)
+                   is_integer_object, is_string_object, is_array)
 
 cimport ccalendar
 from conversion import tz_localize_to_utc, normalize_i8_timestamps
@@ -1103,7 +1102,7 @@ class Timestamp(_Timestamp):
 
 
 # Add the min and max fields at the class level
-cdef int64_t _NS_UPPER_BOUND = INT64_MAX
+cdef int64_t _NS_UPPER_BOUND = np.iinfo(np.int64).max
 # the smallest value we could actually represent is
 #   INT64_MIN + 1 == -9223372036854775807
 # but to allow overflow free conversion with a microsecond resolution
diff --git a/pandas/_libs/tslibs/util.pxd b/pandas/_libs/tslibs/util.pxd
index 0470202ee7d98..0ba61fcc58f46 100644
--- a/pandas/_libs/tslibs/util.pxd
+++ b/pandas/_libs/tslibs/util.pxd
@@ -24,10 +24,10 @@ cdef extern from "Python.h":
     bint PyComplex_Check(object obj) nogil
     bint PyObject_TypeCheck(object obj, PyTypeObject* type) nogil
 
+from numpy cimport int64_t
 
 cdef extern from "numpy/arrayobject.h":
     PyTypeObject PyFloatingArrType_Type
-    ctypedef signed long long int64_t
     int _import_array() except -1
 
 cdef extern from "numpy/ndarrayobject.h":
@@ -43,21 +43,6 @@ cdef extern from  "numpy/npy_common.h":
     int64_t NPY_MIN_INT64
 
 
-cdef extern from "../src/headers/stdint.h":
-    enum: UINT8_MAX
-    enum: UINT16_MAX
-    enum: UINT32_MAX
-    enum: UINT64_MAX
-    enum: INT8_MIN
-    enum: INT8_MAX
-    enum: INT16_MIN
-    enum: INT16_MAX
-    enum: INT32_MAX
-    enum: INT32_MIN
-    enum: INT64_MAX
-    enum: INT64_MIN
-
-
 cdef inline int64_t get_nat():
     return NPY_MIN_INT64
 
diff --git a/pandas/_libs/util.pxd b/pandas/_libs/util.pxd
index 134f34330d8aa..31843a755e7b1 100644
--- a/pandas/_libs/util.pxd
+++ b/pandas/_libs/util.pxd
@@ -14,6 +14,21 @@ cdef extern from "src/numpy_helper.h":
     const char *get_c_string(object) except NULL
 
 
+cdef extern from "src/headers/stdint.h":
+    enum: UINT8_MAX
+    enum: UINT16_MAX
+    enum: UINT32_MAX
+    enum: UINT64_MAX
+    enum: INT8_MIN
+    enum: INT8_MAX
+    enum: INT16_MIN
+    enum: INT16_MAX
+    enum: INT32_MAX
+    enum: INT32_MIN
+    enum: INT64_MAX
+    enum: INT64_MIN
+
+
 ctypedef fused numeric:
     cnp.int8_t
     cnp.int16_t
diff --git a/pandas/tests/tseries/offsets/test_fiscal.py b/pandas/tests/tseries/offsets/test_fiscal.py
index ccd418a69c827..223298dc42544 100644
--- a/pandas/tests/tseries/offsets/test_fiscal.py
+++ b/pandas/tests/tseries/offsets/test_fiscal.py
@@ -13,10 +13,9 @@
 from pandas.tseries.frequencies import get_offset
 from pandas._libs.tslibs.frequencies import INVALID_FREQ_ERR_MSG
 from pandas.tseries.offsets import FY5253Quarter, FY5253
-from pandas._libs.tslibs.offsets import WeekDay
 
 from .common import assert_offset_equal, assert_onOffset
-from .test_offsets import Base
+from .test_offsets import Base, WeekDay
 
 
 def makeFY5253LastOfMonthQuarter(*args, **kwds):
diff --git a/pandas/tests/tseries/offsets/test_offsets.py b/pandas/tests/tseries/offsets/test_offsets.py
index 57b9a281ac0eb..e95f1ba11ad5c 100644
--- a/pandas/tests/tseries/offsets/test_offsets.py
+++ b/pandas/tests/tseries/offsets/test_offsets.py
@@ -17,7 +17,7 @@
 from pandas.core.indexes.datetimes import (
     _to_m8, DatetimeIndex, _daterange_cache)
 import pandas._libs.tslibs.offsets as liboffsets
-from pandas._libs.tslibs.offsets import WeekDay, CacheableOffset
+from pandas._libs.tslibs.offsets import CacheableOffset
 from pandas.tseries.offsets import (BDay, CDay, BQuarterEnd, BMonthEnd,
                                     BusinessHour, WeekOfMonth, CBMonthEnd,
                                     CustomBusinessHour,
@@ -39,6 +39,18 @@
 
 from .common import assert_offset_equal, assert_onOffset
 
+
+class WeekDay(object):
+    # TODO: Remove: This is not used outside of tests
+    MON = 0
+    TUE = 1
+    WED = 2
+    THU = 3
+    FRI = 4
+    SAT = 5
+    SUN = 6
+
+
 ####
 # Misc function tests
 ####