diff --git a/numpy/core/code_generators/genapi.py b/numpy/core/code_generators/genapi.py
index b618dedf562b..a64d62e6eff7 100644
--- a/numpy/core/code_generators/genapi.py
+++ b/numpy/core/code_generators/genapi.py
@@ -52,6 +52,7 @@
              join('multiarray', 'scalarapi.c'),
              join('multiarray', 'sequence.c'),
              join('multiarray', 'shape.c'),
+             join('multiarray', 'strfuncs.c'),
              join('multiarray', 'usertypes.c'),
              join('umath', 'loops.c.src'),
              join('umath', 'ufunc_object.c'),
diff --git a/numpy/core/code_generators/generate_numpy_api.py b/numpy/core/code_generators/generate_numpy_api.py
index 79d774a89b15..b4aeaa277fd8 100644
--- a/numpy/core/code_generators/generate_numpy_api.py
+++ b/numpy/core/code_generators/generate_numpy_api.py
@@ -220,8 +220,13 @@ def do_generate_api(targets, sources):
         multiarray_api_dict[name] = TypeApi(name, index, 'PyTypeObject', api_name)
 
     if len(multiarray_api_dict) != len(multiarray_api_index):
-        raise AssertionError("Multiarray API size mismatch %d %d" %
-                        (len(multiarray_api_dict), len(multiarray_api_index)))
+        keys_dict = set(multiarray_api_dict.keys())
+        keys_index = set(multiarray_api_index.keys())
+        raise AssertionError(
+            "Multiarray API size mismatch - "
+            "index has extra keys {}, dict has extra keys {}"
+            .format(keys_index - keys_dict, keys_dict - keys_index)
+        )
 
     extension_list = []
     for name, index in genapi.order_dict(multiarray_api_index):
diff --git a/numpy/core/setup.py b/numpy/core/setup.py
index e057c56141d3..f268258eea67 100644
--- a/numpy/core/setup.py
+++ b/numpy/core/setup.py
@@ -741,6 +741,7 @@ def get_mathlib_info(*args):
             join('src', 'multiarray', 'scalartypes.h'),
             join('src', 'multiarray', 'sequence.h'),
             join('src', 'multiarray', 'shape.h'),
+            join('src', 'multiarray', 'strfuncs.h'),
             join('src', 'multiarray', 'ucsnarrow.h'),
             join('src', 'multiarray', 'usertypes.h'),
             join('src', 'multiarray', 'vdot.h'),
@@ -814,6 +815,7 @@ def get_mathlib_info(*args):
             join('src', 'multiarray', 'shape.c'),
             join('src', 'multiarray', 'scalarapi.c'),
             join('src', 'multiarray', 'scalartypes.c.src'),
+            join('src', 'multiarray', 'strfuncs.c'),
             join('src', 'multiarray', 'temp_elide.c'),
             join('src', 'multiarray', 'usertypes.c'),
             join('src', 'multiarray', 'ucsnarrow.c'),
diff --git a/numpy/core/src/multiarray/arrayobject.c b/numpy/core/src/multiarray/arrayobject.c
index 062fa8879599..0e655d80c1d8 100644
--- a/numpy/core/src/multiarray/arrayobject.c
+++ b/numpy/core/src/multiarray/arrayobject.c
@@ -53,6 +53,7 @@ maintainer email:  oliphant.travis@ieee.org
 #include "alloc.h"
 #include "mem_overlap.h"
 #include "numpyos.h"
+#include "strfuncs.h"
 
 #include "binop_override.h"
 
@@ -433,93 +434,6 @@ array_dealloc(PyArrayObject *self)
     Py_TYPE(self)->tp_free((PyObject *)self);
 }
 
-/*
- * Extend string. On failure, returns NULL and leaves *strp alone.
- * XXX we do this in multiple places; time for a string library?
- */
-static char *
-extend(char **strp, Py_ssize_t n, Py_ssize_t *maxp)
-{
-    char *str = *strp;
-    Py_ssize_t new_cap;
-
-    if (n >= *maxp - 16) {
-        new_cap = *maxp * 2;
-
-        if (new_cap <= *maxp) {     /* overflow */
-            return NULL;
-        }
-        str = PyArray_realloc(*strp, new_cap);
-        if (str != NULL) {
-            *strp = str;
-            *maxp = new_cap;
-        }
-    }
-    return str;
-}
-
-static int
-dump_data(char **string, Py_ssize_t *n, Py_ssize_t *max_n, char *data, int nd,
-          npy_intp *dimensions, npy_intp *strides, PyArrayObject* self)
-{
-    PyArray_Descr *descr=PyArray_DESCR(self);
-    PyObject *op = NULL, *sp = NULL;
-    char *ostring;
-    npy_intp i, N, ret = 0;
-
-#define CHECK_MEMORY do {                           \
-        if (extend(string, *n, max_n) == NULL) {    \
-            ret = -1;                               \
-            goto end;                               \
-        }                                           \
-    } while (0)
-
-    if (nd == 0) {
-        if ((op = descr->f->getitem(data, self)) == NULL) {
-            return -1;
-        }
-        sp = PyObject_Repr(op);
-        if (sp == NULL) {
-            ret = -1;
-            goto end;
-        }
-        ostring = PyString_AsString(sp);
-        N = PyString_Size(sp)*sizeof(char);
-        *n += N;
-        CHECK_MEMORY;
-        memmove(*string + (*n - N), ostring, N);
-    }
-    else {
-        CHECK_MEMORY;
-        (*string)[*n] = '[';
-        *n += 1;
-        for (i = 0; i < dimensions[0]; i++) {
-            if (dump_data(string, n, max_n,
-                          data + (*strides)*i,
-                          nd - 1, dimensions + 1,
-                          strides + 1, self) < 0) {
-                return -1;
-            }
-            CHECK_MEMORY;
-            if (i < dimensions[0] - 1) {
-                (*string)[*n] = ',';
-                (*string)[*n+1] = ' ';
-                *n += 2;
-            }
-        }
-        CHECK_MEMORY;
-        (*string)[*n] = ']';
-        *n += 1;
-    }
-
-#undef CHECK_MEMORY
-
-end:
-    Py_XDECREF(op);
-    Py_XDECREF(sp);
-    return ret;
-}
-
 /*NUMPY_API
  * Prints the raw data of the ndarray in a form useful for debugging
  * low-level C issues.
@@ -582,72 +496,6 @@ PyArray_DebugPrint(PyArrayObject *obj)
     fflush(stdout);
 }
 
-static PyObject *
-array_repr_builtin(PyArrayObject *self, int repr)
-{
-    PyObject *ret;
-    char *string;
-    /* max_n initial value is arbitrary, dump_data will extend it */
-    Py_ssize_t n = 0, max_n = PyArray_NBYTES(self) * 4 + 7;
-
-    if ((string = PyArray_malloc(max_n)) == NULL) {
-        return PyErr_NoMemory();
-    }
-
-    if (dump_data(&string, &n, &max_n, PyArray_DATA(self),
-                  PyArray_NDIM(self), PyArray_DIMS(self),
-                  PyArray_STRIDES(self), self) < 0) {
-        PyArray_free(string);
-        return NULL;
-    }
-
-    if (repr) {
-        if (PyArray_ISEXTENDED(self)) {
-            ret = PyUString_FromFormat("array(%s, '%c%d')",
-                                       string,
-                                       PyArray_DESCR(self)->type,
-                                       PyArray_DESCR(self)->elsize);
-        }
-        else {
-            ret = PyUString_FromFormat("array(%s, '%c')",
-                                       string,
-                                       PyArray_DESCR(self)->type);
-        }
-    }
-    else {
-        ret = PyUString_FromStringAndSize(string, n);
-    }
-
-    PyArray_free(string);
-    return ret;
-}
-
-static PyObject *PyArray_StrFunction = NULL;
-static PyObject *PyArray_ReprFunction = NULL;
-
-/*NUMPY_API
- * Set the array print function to be a Python function.
- */
-NPY_NO_EXPORT void
-PyArray_SetStringFunction(PyObject *op, int repr)
-{
-    if (repr) {
-        /* Dispose of previous callback */
-        Py_XDECREF(PyArray_ReprFunction);
-        /* Add a reference to new callback */
-        Py_XINCREF(op);
-        /* Remember new callback */
-        PyArray_ReprFunction = op;
-    }
-    else {
-        /* Dispose of previous callback */
-        Py_XDECREF(PyArray_StrFunction);
-        /* Add a reference to new callback */
-        Py_XINCREF(op);
-        /* Remember new callback */
-        PyArray_StrFunction = op;
-    }
-}
 
 /*NUMPY_API
  * This function is scheduled to be removed
@@ -660,39 +508,6 @@ PyArray_SetDatetimeParseFunction(PyObject *op)
 }
 
 
-static PyObject *
-array_repr(PyArrayObject *self)
-{
-    PyObject *s, *arglist;
-
-    if (PyArray_ReprFunction == NULL) {
-        s = array_repr_builtin(self, 1);
-    }
-    else {
-        arglist = Py_BuildValue("(O)", self);
-        s = PyEval_CallObject(PyArray_ReprFunction, arglist);
-        Py_DECREF(arglist);
-    }
-    return s;
-}
-
-static PyObject *
-array_str(PyArrayObject *self)
-{
-    PyObject *s, *arglist;
-
-    if (PyArray_StrFunction == NULL) {
-        s = array_repr_builtin(self, 0);
-    }
-    else {
-        arglist = Py_BuildValue("(O)", self);
-        s = PyEval_CallObject(PyArray_StrFunction, arglist);
-        Py_DECREF(arglist);
-    }
-    return s;
-}
-
-
 
 /*NUMPY_API
  */
diff --git a/numpy/core/src/multiarray/strfuncs.c b/numpy/core/src/multiarray/strfuncs.c
new file mode 100644
index 000000000000..5a0d203351a7
--- /dev/null
+++ b/numpy/core/src/multiarray/strfuncs.c
@@ -0,0 +1,200 @@
+#define NPY_NO_DEPRECATED_API NPY_API_VERSION
+#define _MULTIARRAYMODULE
+
+#include <Python.h>
+#include <numpy/arrayobject.h>
+
+#include "npy_pycompat.h"
+
+#include "strfuncs.h"
+
+static PyObject *PyArray_StrFunction = NULL;
+static PyObject *PyArray_ReprFunction = NULL;
+
+/*NUMPY_API
+ * Set the array print function to be a Python function.
+ */
+NPY_NO_EXPORT void
+PyArray_SetStringFunction(PyObject *op, int repr)
+{
+    if (repr) {
+        /* Dispose of previous callback */
+        Py_XDECREF(PyArray_ReprFunction);
+        /* Add a reference to new callback */
+        Py_XINCREF(op);
+        /* Remember new callback */
+        PyArray_ReprFunction = op;
+    }
+    else {
+        /* Dispose of previous callback */
+        Py_XDECREF(PyArray_StrFunction);
+        /* Add a reference to new callback */
+        Py_XINCREF(op);
+        /* Remember new callback */
+        PyArray_StrFunction = op;
+    }
+}
+
+
+/*
+ * Extend string. On failure, returns NULL and leaves *strp alone.
+ * XXX we do this in multiple places; time for a string library?
+ */
+static char *
+extend(char **strp, Py_ssize_t n, Py_ssize_t *maxp)
+{
+    char *str = *strp;
+    Py_ssize_t new_cap;
+
+    if (n >= *maxp - 16) {
+        new_cap = *maxp * 2;
+
+        if (new_cap <= *maxp) {     /* overflow */
+            return NULL;
+        }
+        str = PyArray_realloc(*strp, new_cap);
+        if (str != NULL) {
+            *strp = str;
+            *maxp = new_cap;
+        }
+    }
+    return str;
+}
+
+
+static int
+dump_data(char **string, Py_ssize_t *n, Py_ssize_t *max_n, char *data, int nd,
+          npy_intp *dimensions, npy_intp *strides, PyArrayObject* self)
+{
+    PyArray_Descr *descr=PyArray_DESCR(self);
+    PyObject *op = NULL, *sp = NULL;
+    char *ostring;
+    npy_intp i, N, ret = 0;
+
+#define CHECK_MEMORY do {                           \
+        if (extend(string, *n, max_n) == NULL) {    \
+            ret = -1;                               \
+            goto end;                               \
+        }                                           \
+    } while (0)
+
+    if (nd == 0) {
+        if ((op = descr->f->getitem(data, self)) == NULL) {
+            return -1;
+        }
+        sp = PyObject_Repr(op);
+        if (sp == NULL) {
+            ret = -1;
+            goto end;
+        }
+        ostring = PyString_AsString(sp);
+        N = PyString_Size(sp)*sizeof(char);
+        *n += N;
+        CHECK_MEMORY;
+        memmove(*string + (*n - N), ostring, N);
+    }
+    else {
+        CHECK_MEMORY;
+        (*string)[*n] = '[';
+        *n += 1;
+        for (i = 0; i < dimensions[0]; i++) {
+            if (dump_data(string, n, max_n,
+                          data + (*strides)*i,
+                          nd - 1, dimensions + 1,
+                          strides + 1, self) < 0) {
+                return -1;
+            }
+            CHECK_MEMORY;
+            if (i < dimensions[0] - 1) {
+                (*string)[*n] = ',';
+                (*string)[*n+1] = ' ';
+                *n += 2;
+            }
+        }
+        CHECK_MEMORY;
+        (*string)[*n] = ']';
+        *n += 1;
+    }
+
+#undef CHECK_MEMORY
+
+end:
+    Py_XDECREF(op);
+    Py_XDECREF(sp);
+    return ret;
+}
+
+
+static PyObject *
+array_repr_builtin(PyArrayObject *self, int repr)
+{
+    PyObject *ret;
+    char *string;
+    /* max_n initial value is arbitrary, dump_data will extend it */
+    Py_ssize_t n = 0, max_n = PyArray_NBYTES(self) * 4 + 7;
+
+    if ((string = PyArray_malloc(max_n)) == NULL) {
+        return PyErr_NoMemory();
+    }
+
+    if (dump_data(&string, &n, &max_n, PyArray_DATA(self),
+                  PyArray_NDIM(self), PyArray_DIMS(self),
+                  PyArray_STRIDES(self), self) < 0) {
+        PyArray_free(string);
+        return NULL;
+    }
+
+    if (repr) {
+        if (PyArray_ISEXTENDED(self)) {
+            ret = PyUString_FromFormat("array(%s, '%c%d')",
+                                       string,
+                                       PyArray_DESCR(self)->type,
+                                       PyArray_DESCR(self)->elsize);
+        }
+        else {
+            ret = PyUString_FromFormat("array(%s, '%c')",
+                                       string,
+                                       PyArray_DESCR(self)->type);
+        }
+    }
+    else {
+        ret = PyUString_FromStringAndSize(string, n);
+    }
+
+    PyArray_free(string);
+    return ret;
+}
+
+
+NPY_NO_EXPORT PyObject *
+array_repr(PyArrayObject *self)
+{
+    PyObject *s, *arglist;
+
+    if (PyArray_ReprFunction == NULL) {
+        s = array_repr_builtin(self, 1);
+    }
+    else {
+        arglist = Py_BuildValue("(O)", self);
+        s = PyEval_CallObject(PyArray_ReprFunction, arglist);
+        Py_DECREF(arglist);
+    }
+    return s;
+}
+
+
+NPY_NO_EXPORT PyObject *
+array_str(PyArrayObject *self)
+{
+    PyObject *s, *arglist;
+
+    if (PyArray_StrFunction == NULL) {
+        s = array_repr_builtin(self, 0);
+    }
+    else {
+        arglist = Py_BuildValue("(O)", self);
+        s = PyEval_CallObject(PyArray_StrFunction, arglist);
+        Py_DECREF(arglist);
+    }
+    return s;
+}
diff --git a/numpy/core/src/multiarray/strfuncs.h b/numpy/core/src/multiarray/strfuncs.h
new file mode 100644
index 000000000000..8e80897c2ccb
--- /dev/null
+++ b/numpy/core/src/multiarray/strfuncs.h
@@ -0,0 +1,13 @@
+#ifndef _NPY_ARRAY_STRFUNCS_H_
+#define _NPY_ARRAY_STRFUNCS_H_
+
+NPY_NO_EXPORT void
+PyArray_SetStringFunction(PyObject *op, int repr);
+
+NPY_NO_EXPORT PyObject *
+array_repr(PyArrayObject *self);
+
+NPY_NO_EXPORT PyObject *
+array_str(PyArrayObject *self);
+
+#endif