From 193f5c09b3598d7bcb4de47108d93514176e3eca Mon Sep 17 00:00:00 2001
From: MomIsBestFriend <>
Date: Fri, 13 Mar 2020 16:25:50 +0200
Subject: [PATCH 1/3] PERF: Using Numpy C-API arange

---
 pandas/_libs/internals.pyx | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/internals.pyx b/pandas/_libs/internals.pyx
index 437406cbbd819..7d45233d92855 100644
--- a/pandas/_libs/internals.pyx
+++ b/pandas/_libs/internals.pyx
@@ -7,7 +7,9 @@ cdef extern from "Python.h":
     Py_ssize_t PY_SSIZE_T_MAX
 
 import numpy as np
-from numpy cimport int64_t
+cimport numpy as cnp
+from numpy cimport NPY_INT64, int64_t
+cnp.import_array()
 
 from pandas._libs.algos import ensure_int64
 
@@ -105,7 +107,7 @@ cdef class BlockPlacement:
             Py_ssize_t start, stop, end, _
         if not self._has_array:
             start, stop, step, _ = slice_get_indices_ex(self._as_slice)
-            self._as_array = np.arange(start, stop, step, dtype=np.int64)
+            self._as_array = cnp.PyArray_Arange(start, stop, step, NPY_INT64)
             self._has_array = True
         return self._as_array
 

From addde1e5cf5a3529724cbce7888b1e86d81e60cc Mon Sep 17 00:00:00 2001
From: MomIsBestFriend <>
Date: Fri, 13 Mar 2020 18:28:59 +0200
Subject: [PATCH 2/3] Added note

REF:
https://github.com/pandas-dev/pandas/pull/32681#discussion_r392334261
---
 pandas/_libs/internals.pyx | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/pandas/_libs/internals.pyx b/pandas/_libs/internals.pyx
index 7d45233d92855..378fc9bb747cd 100644
--- a/pandas/_libs/internals.pyx
+++ b/pandas/_libs/internals.pyx
@@ -107,6 +107,8 @@ cdef class BlockPlacement:
             Py_ssize_t start, stop, end, _
         if not self._has_array:
             start, stop, step, _ = slice_get_indices_ex(self._as_slice)
+            # NOTE: this is the C-optimized equivalent of
+            # np.arange(start, stop, step, dtype=np.int64)
             self._as_array = cnp.PyArray_Arange(start, stop, step, NPY_INT64)
             self._has_array = True
         return self._as_array

From c1f6688f08caa51723ff1bb5e69e52a8cf35d57a Mon Sep 17 00:00:00 2001
From: MomIsBestFriend <>
Date: Fri, 13 Mar 2020 19:02:01 +0200
Subject: [PATCH 3/3] Added extra space at the beggining of the comment block

REF:
https://github.com/pandas-dev/pandas/pull/32681#discussion_r392354159
---
 pandas/_libs/internals.pyx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/_libs/internals.pyx b/pandas/_libs/internals.pyx
index 378fc9bb747cd..7f861e587e637 100644
--- a/pandas/_libs/internals.pyx
+++ b/pandas/_libs/internals.pyx
@@ -108,7 +108,7 @@ cdef class BlockPlacement:
         if not self._has_array:
             start, stop, step, _ = slice_get_indices_ex(self._as_slice)
             # NOTE: this is the C-optimized equivalent of
-            # np.arange(start, stop, step, dtype=np.int64)
+            #  np.arange(start, stop, step, dtype=np.int64)
             self._as_array = cnp.PyArray_Arange(start, stop, step, NPY_INT64)
             self._has_array = True
         return self._as_array