diff --git a/pandas/core/strings/accessor.py b/pandas/core/strings/accessor.py
index b854338c2d1d7..8ebd84226b5e3 100644
--- a/pandas/core/strings/accessor.py
+++ b/pandas/core/strings/accessor.py
@@ -428,7 +428,7 @@ def cons_row(x):
                 result.name = name
             return result
 
-    def _get_series_list(self, others):
+    def _get_series_list(self, others) -> list[Series]:
         """
         Auxiliary function for :meth:`str.cat`. Turn potentially mixed input
         into a list of Series (elements without an index must match the length
@@ -479,8 +479,8 @@ def _get_series_list(self, others):
                     for x in others
                 ):
                     los: list[Series] = []
-                    while others:  # iterate through list and append each element
-                        los = los + self._get_series_list(others.pop(0))
+                    for other in others:
+                        los.extend(self._get_series_list(other))
                     return los
                 # ... or just strings
                 elif all(not is_list_like(x) for x in others):
diff --git a/pandas/plotting/_matplotlib/tools.py b/pandas/plotting/_matplotlib/tools.py
index 8ee75e7fe553e..d152735842f45 100644
--- a/pandas/plotting/_matplotlib/tools.py
+++ b/pandas/plotting/_matplotlib/tools.py
@@ -1,7 +1,11 @@
 # being a bit too dynamic
 from __future__ import annotations
 
-from math import ceil
+from math import (
+    ceil,
+    floor,
+    log2,
+)
 from typing import TYPE_CHECKING
 import warnings
 
@@ -126,9 +130,7 @@ def _get_layout(
     try:
         return layouts[nplots]
     except KeyError:
-        k = 1
-        while k**2 < nplots:
-            k += 1
+        k = floor(log2(nplots)) + 1
 
         if (k - 1) * k >= nplots:
             return k, (k - 1)