Make more of numpy_helper unnecessary (pandas-dev#22344)

pandas/_libs/index.pyx

@@ -319,15 +319,14 @@ cdef class IndexEngine:
         # form the set of the results (like ismember)
         members = np.empty(n, dtype=np.uint8)
         for i in range(n):
-            val = util.get_value_1d(values, i)
+            val = values[i]
             if val in stargets:
                 if val not in d:
                     d[val] = []
                 d[val].append(i)
 
         for i in range(n_t):
-
-            val = util.get_value_1d(targets, i)
+            val = targets[i]
 
             # found
             if val in d:

pandas/_libs/lib.pyx

@@ -1153,7 +1153,7 @@ def infer_dtype(object value, bint skipna=False):
 
     # try to use a valid value
     for i in range(n):
-        val = util.get_value_1d(values, i)
+        val = values[i]
 
         # do not use is_nul_datetimelike to keep
         # np.datetime64('nat') and np.timedelta64('nat')
@@ -1240,7 +1240,7 @@ def infer_dtype(object value, bint skipna=False):
             return 'interval'
 
     for i in range(n):
-        val = util.get_value_1d(values, i)
+        val = values[i]
         if (util.is_integer_object(val) and
                 not util.is_timedelta64_object(val) and
                 not util.is_datetime64_object(val)):
@@ -2255,7 +2255,7 @@ def fast_multiget(dict mapping, ndarray keys, default=np.nan):
     keys = getattr(keys, 'values', keys)
 
     for i in range(n):
-        val = util.get_value_1d(keys, i)
+        val = keys[i]
         if val in mapping:
             output[i] = mapping[val]
         else:

pandas/_libs/src/numpy_helper.h

@@ -28,20 +28,4 @@ PANDAS_INLINE PyObject* get_value_1d(PyArrayObject* ap, Py_ssize_t i) {
     return PyArray_Scalar(item, PyArray_DESCR(ap), (PyObject*)ap);
 }
 
-// returns ASCII or UTF8 (py3) view on python str
-// python object owns memory, should not be freed
-PANDAS_INLINE const char* get_c_string(PyObject* obj) {
-#if PY_VERSION_HEX >= 0x03000000
-    return PyUnicode_AsUTF8(obj);
-#else
-    return PyString_AsString(obj);
-#endif
-}
-
-void set_array_not_contiguous(PyArrayObject* ao) {
-    // Numpy>=1.8-compliant equivalent to:
-    //  ao->flags &= ~(NPY_ARRAY_C_CONTIGUOUS | NPY_ARRAY_F_CONTIGUOUS);
-    PyArray_CLEARFLAGS(ao, (NPY_ARRAY_C_CONTIGUOUS | NPY_ARRAY_F_CONTIGUOUS));
-}
-
 #endif  // PANDAS__LIBS_SRC_NUMPY_HELPER_H_

pandas/_libs/util.pxd

@@ -5,13 +5,34 @@ from cython cimport Py_ssize_t
 cimport numpy as cnp
 from numpy cimport ndarray
 
+cdef extern from "numpy/ndarraytypes.h":
+    void PyArray_CLEARFLAGS(ndarray arr, int flags) nogil
+
+
+cdef extern from "numpy/arrayobject.h":
+    enum:
+        NPY_ARRAY_C_CONTIGUOUS
+        NPY_ARRAY_F_CONTIGUOUS
+
+
+cdef extern from *:
+    """
+    // returns ASCII or UTF8 (py3) view on python str
+    // python object owns memory, should not be freed
+    static const char* get_c_string(PyObject* obj) {
+    #if PY_VERSION_HEX >= 0x03000000
+        return PyUnicode_AsUTF8(obj);
+    #else
+        return PyString_AsString(obj);
+    #endif
+    }
+    """
+    const char *get_c_string(object) except NULL
 
-cdef extern from "src/numpy_helper.h":
-    void set_array_not_contiguous(ndarray ao)
 
+cdef extern from "src/numpy_helper.h":
     int assign_value_1d(ndarray, Py_ssize_t, object) except -1
     object get_value_1d(ndarray, Py_ssize_t)
-    const char *get_c_string(object) except NULL
 
 
 cdef extern from "src/headers/stdint.h":
@@ -44,6 +65,13 @@ ctypedef fused numeric:
     cnp.float64_t
 
 
+cdef inline void set_array_not_contiguous(ndarray ao) nogil:
+    # Numpy>=1.8-compliant equivalent to:
+    # ao->flags &= ~(NPY_ARRAY_C_CONTIGUOUS | NPY_ARRAY_F_CONTIGUOUS);
+    PyArray_CLEARFLAGS(ao,
+                       (NPY_ARRAY_C_CONTIGUOUS | NPY_ARRAY_F_CONTIGUOUS))
+
+
 cdef inline object get_value_at(ndarray arr, object loc):
     cdef:
         Py_ssize_t i, sz