From cc8497eaf3cefb67e823b3f0e2e8d86ce3e3731b Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Mon, 18 Sep 2023 11:19:15 -0400
Subject: [PATCH 1/5] faster ensure_string_array

---
 pandas/_libs/lib.pyx | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pandas/_libs/lib.pyx b/pandas/_libs/lib.pyx
index 0c0610f72044e..f7f4a9f676fdf 100644
--- a/pandas/_libs/lib.pyx
+++ b/pandas/_libs/lib.pyx
@@ -776,6 +776,7 @@ cpdef ndarray[object] ensure_string_array(
     cdef:
         Py_ssize_t i = 0, n = len(arr)
         bint already_copied = True
+        ndarray[object] newarr
 
     if hasattr(arr, "to_numpy"):
 
@@ -800,8 +801,9 @@ cpdef ndarray[object] ensure_string_array(
         # short-circuit, all elements are str
         return result
 
+    newarr = np.asarray(arr, dtype=object)
     for i in range(n):
-        val = arr[i]
+        val = newarr[i]
 
         if isinstance(val, str):
             continue

From 7a823afa436e68501159316b6aab61ce57e1a845 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Mon, 18 Sep 2023 12:23:43 -0400
Subject: [PATCH 2/5] faster map_infer_mask

---
 pandas/_libs/lib.pyx | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/pandas/_libs/lib.pyx b/pandas/_libs/lib.pyx
index f7f4a9f676fdf..910e6ad972857 100644
--- a/pandas/_libs/lib.pyx
+++ b/pandas/_libs/lib.pyx
@@ -2833,9 +2833,14 @@ NoDefault = Literal[_NoDefault.no_default]
 
 @cython.boundscheck(False)
 @cython.wraparound(False)
-def map_infer_mask(ndarray arr, object f, const uint8_t[:] mask, bint convert=True,
-                   object na_value=no_default, cnp.dtype dtype=np.dtype(object)
-                   ) -> np.ndarray:
+def map_infer_mask(
+        ndarray[object] arr,
+        object f,
+        const uint8_t[:] mask,
+        bint convert=True,
+        object na_value=no_default,
+        cnp.dtype dtype=np.dtype(object)
+) -> np.ndarray:
     """
     Substitute for np.vectorize with pandas-friendly dtype inference.
 

From c2f4cd155ee5eeebc5917f35952658335389d2d2 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Mon, 18 Sep 2023 13:44:16 -0400
Subject: [PATCH 3/5] non-optimized float path

---
 pandas/_libs/lib.pyx | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/pandas/_libs/lib.pyx b/pandas/_libs/lib.pyx
index 910e6ad972857..65126e18627a4 100644
--- a/pandas/_libs/lib.pyx
+++ b/pandas/_libs/lib.pyx
@@ -801,6 +801,29 @@ cpdef ndarray[object] ensure_string_array(
         # short-circuit, all elements are str
         return result
 
+    from pandas.core.dtypes.common import is_float_dtype
+    if is_float_dtype(arr.dtype):  # non-optimized path
+        print("going non-optimal route")
+        for i in range(n):
+            val = arr[i]
+
+            if not already_copied:
+                result = result.copy()
+                already_copied = True
+
+            if not checknull(val):
+                # f"{val}" is not always equivalent to str(val) for floats
+                result[i] = str(val)
+            else:
+                if convert_na_value:
+                    val = na_value
+                if skipna:
+                    result[i] = val
+                else:
+                    result[i] = f"{val}"
+
+        return result
+
     newarr = np.asarray(arr, dtype=object)
     for i in range(n):
         val = newarr[i]

From d9062bf893e01e7c2dbef95d79d7abcdd0ed6870 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Mon, 18 Sep 2023 14:40:22 -0400
Subject: [PATCH 4/5] remove print

---
 pandas/_libs/lib.pyx | 1 -
 1 file changed, 1 deletion(-)

diff --git a/pandas/_libs/lib.pyx b/pandas/_libs/lib.pyx
index 65126e18627a4..bee90e9df18b3 100644
--- a/pandas/_libs/lib.pyx
+++ b/pandas/_libs/lib.pyx
@@ -803,7 +803,6 @@ cpdef ndarray[object] ensure_string_array(
 
     from pandas.core.dtypes.common import is_float_dtype
     if is_float_dtype(arr.dtype):  # non-optimized path
-        print("going non-optimal route")
         for i in range(n):
             val = arr[i]
 

From affc3490285a0a23adb6cfe3c0f431b1063ce5e4 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Mon, 18 Sep 2023 18:01:10 -0400
Subject: [PATCH 5/5] feedback

---
 pandas/_libs/lib.pyx | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/pandas/_libs/lib.pyx b/pandas/_libs/lib.pyx
index bee90e9df18b3..23c8066b973f8 100644
--- a/pandas/_libs/lib.pyx
+++ b/pandas/_libs/lib.pyx
@@ -801,8 +801,7 @@ cpdef ndarray[object] ensure_string_array(
         # short-circuit, all elements are str
         return result
 
-    from pandas.core.dtypes.common import is_float_dtype
-    if is_float_dtype(arr.dtype):  # non-optimized path
+    if arr.dtype.kind == "f":  # non-optimized path
         for i in range(n):
             val = arr[i]