From 462bfec580755011ff2a4508ad036cbc7c8e9324 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A9n=C3=A9dikt=20Tran?=
 <10796600+picnixz@users.noreply.github.com>
Date: Wed, 9 Jul 2025 15:41:24 +0200
Subject: [PATCH] fix `IndexError` in `pydoc.replace`

---
 Lib/pydoc.py                                              | 8 +++++---
 .../2025-07-12-13-21-34.gh-issue-136572.PLssWH.rst        | 3 +++
 2 files changed, 8 insertions(+), 3 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2025-07-12-13-21-34.gh-issue-136572.PLssWH.rst

diff --git a/Lib/pydoc.py b/Lib/pydoc.py
index d508fb70ea429e..8a3eaaf4424045 100644
--- a/Lib/pydoc.py
+++ b/Lib/pydoc.py
@@ -262,9 +262,11 @@ def isdata(object):
 
 def replace(text, *pairs):
     """Do a series of global replacements on a string."""
-    while pairs:
-        text = pairs[1].join(text.split(pairs[0]))
-        pairs = pairs[2:]
+    if len(pairs) % 2:
+        # len(pairs) must be even, so len(pairs) + 1 must be odd
+        raise TypeError("an odd number of arguments must be given")
+    for ind in range(0, len(pairs), 2):
+        text = pairs[ind + 1].join(text.split(pairs[ind]))
     return text
 
 def cram(text, maxlen):
diff --git a/Misc/NEWS.d/next/Library/2025-07-12-13-21-34.gh-issue-136572.PLssWH.rst b/Misc/NEWS.d/next/Library/2025-07-12-13-21-34.gh-issue-136572.PLssWH.rst
new file mode 100644
index 00000000000000..726cc95e43c92e
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-07-12-13-21-34.gh-issue-136572.PLssWH.rst
@@ -0,0 +1,3 @@
+:func:`!pydoc.replace` now raises a :exc:`TypeError` instead of an
+:exc:`IndexError` when the number of variadic arguments is odd (or
+equivalently, if the total number of arguments is even).