From 6685a61413dd30204a5bd0f70e6bd891a29557ef Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alexander=20B=C3=B6hn?= <fish2000@gmail.com>
Date: Mon, 3 Feb 2020 21:11:28 -0500
Subject: [PATCH 1/2] =?UTF-8?q?bpo-39549:=20reprlib.Repr=20uses=20a=20?=
 =?UTF-8?q?=E2=80=9Cfillvalue=E2=80=9D=20attribute?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Whereas the code for `reprlib.Repr` had previously used a hardcoded
string value of '...', this PR updates it to use of a “fillvalue”
attribute, whose value defaults to '...' and can be reset in either
individual `reprlib.Repr` instances or in subclasses thereof.

A new assert has been added to `test_reprlib.py` to verify the new
attributes’ functionality.
---
 Lib/reprlib.py                                | 24 ++++++++++++-------
 Lib/test/test_reprlib.py                      |  7 ++++++
 .../2020-02-03-21-18-31.bpo-39549.l4a8uH.rst  |  4 ++++
 3 files changed, 26 insertions(+), 9 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2020-02-03-21-18-31.bpo-39549.l4a8uH.rst

diff --git a/Lib/reprlib.py b/Lib/reprlib.py
index 616b3439b5de30..f3518df105e418 100644
--- a/Lib/reprlib.py
+++ b/Lib/reprlib.py
@@ -36,6 +36,7 @@ def wrapper(self):
 class Repr:
 
     def __init__(self):
+        self.fillvalue = '...'
         self.maxlevel = 6
         self.maxtuple = 6
         self.maxlist = 6
@@ -64,14 +65,16 @@ def repr1(self, x, level):
     def _repr_iterable(self, x, level, left, right, maxiter, trail=''):
         n = len(x)
         if level <= 0 and n:
-            s = '...'
+            s = self.fillvalue
         else:
             newlevel = level - 1
             repr1 = self.repr1
             pieces = [repr1(elem, newlevel) for elem in islice(x, maxiter)]
-            if n > maxiter:  pieces.append('...')
+            if n > maxiter:
+                pieces.append(self.fillvalue)
             s = ', '.join(pieces)
-            if n == 1 and trail:  right = trail + right
+            if n == 1 and trail:
+                right = trail + right
         return '%s%s%s' % (left, s, right)
 
     def repr_tuple(self, x, level):
@@ -104,8 +107,10 @@ def repr_deque(self, x, level):
 
     def repr_dict(self, x, level):
         n = len(x)
-        if n == 0: return '{}'
-        if level <= 0: return '{...}'
+        if n == 0:
+            return '{}'
+        if level <= 0:
+            return '{' + self.fillvalue + '}'
         newlevel = level - 1
         repr1 = self.repr1
         pieces = []
@@ -113,7 +118,8 @@ def repr_dict(self, x, level):
             keyrepr = repr1(key, newlevel)
             valrepr = repr1(x[key], newlevel)
             pieces.append('%s: %s' % (keyrepr, valrepr))
-        if n > self.maxdict: pieces.append('...')
+        if n > self.maxdict:
+            pieces.append(self.fillvalue)
         s = ', '.join(pieces)
         return '{%s}' % (s,)
 
@@ -123,7 +129,7 @@ def repr_str(self, x, level):
             i = max(0, (self.maxstring-3)//2)
             j = max(0, self.maxstring-3-i)
             s = builtins.repr(x[:i] + x[len(x)-j:])
-            s = s[:i] + '...' + s[len(s)-j:]
+            s = s[:i] + self.fillvalue + s[len(s)-j:]
         return s
 
     def repr_int(self, x, level):
@@ -131,7 +137,7 @@ def repr_int(self, x, level):
         if len(s) > self.maxlong:
             i = max(0, (self.maxlong-3)//2)
             j = max(0, self.maxlong-3-i)
-            s = s[:i] + '...' + s[len(s)-j:]
+            s = s[:i] + self.fillvalue + s[len(s)-j:]
         return s
 
     def repr_instance(self, x, level):
@@ -144,7 +150,7 @@ def repr_instance(self, x, level):
         if len(s) > self.maxother:
             i = max(0, (self.maxother-3)//2)
             j = max(0, self.maxother-3-i)
-            s = s[:i] + '...' + s[len(s)-j:]
+            s = s[:i] + self.fillvalue + s[len(s)-j:]
         return s
 
 
diff --git a/Lib/test/test_reprlib.py b/Lib/test/test_reprlib.py
index 0555b71bbf21af..aa326399ab2247 100644
--- a/Lib/test/test_reprlib.py
+++ b/Lib/test/test_reprlib.py
@@ -51,6 +51,13 @@ def test_tuple(self):
         expected = repr(t3)[:-2] + "...)"
         eq(r2.repr(t3), expected)
 
+        # modified fillvalue:
+        r3 = Repr()
+        r3.fillvalue = '+++'
+        r3.maxtuple = 2
+        expected = repr(t3)[:-2] + "+++)"
+        eq(r3.repr(t3), expected)
+
     def test_container(self):
         from array import array
         from collections import deque
diff --git a/Misc/NEWS.d/next/Library/2020-02-03-21-18-31.bpo-39549.l4a8uH.rst b/Misc/NEWS.d/next/Library/2020-02-03-21-18-31.bpo-39549.l4a8uH.rst
new file mode 100644
index 00000000000000..91d63a96763cee
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-02-03-21-18-31.bpo-39549.l4a8uH.rst
@@ -0,0 +1,4 @@
+Whereas the code for reprlib.Repr had previously used a hardcoded string
+value of '...', this PR updates it to use of a “fillvalue” attribute, whose
+value defaults to '...' and can be reset in either individual reprlib.Repr
+instances or in subclasses thereof.

From fe900355fff2ab729f2185c975210691b05e7c7e Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <raymond.hettinger@gmail.com>
Date: Tue, 21 Sep 2021 14:25:17 -0500
Subject: [PATCH 2/2] Add to the main docs

---
 Doc/library/reprlib.rst | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Doc/library/reprlib.rst b/Doc/library/reprlib.rst
index 1a0c1b0dcd1aa9..4b37c5ba60f4e6 100644
--- a/Doc/library/reprlib.rst
+++ b/Doc/library/reprlib.rst
@@ -76,6 +76,14 @@ size limits for the representations of different object types,  and methods
 which format specific object types.
 
 
+.. attribute:: Repr.fillvalue
+
+   This string is displayed for recursive references. It defaults to
+   ``...``.
+
+   .. versionadded:: 3.11
+
+
 .. attribute:: Repr.maxlevel
 
    Depth limit on the creation of recursive representations.  The default is ``6``.