BUG: pretty print all Mappings, not just dicts (#57915)

This was discovered in ibis-project/ibis#8693

Author: NickCrews

doc/source/whatsnew/v3.0.0.rst

@@ -357,6 +357,7 @@ MultiIndex
 I/O
 ^^^
 - Bug in :meth:`DataFrame.to_excel` when writing empty :class:`DataFrame` with :class:`MultiIndex` on both axes (:issue:`57696`)
+- Now all ``Mapping`` s are pretty printed correctly. Before only literal ``dict`` s were. (:issue:`57915`)
 -
 -
 

pandas/io/formats/printing.py

@@ -187,8 +187,8 @@ def pprint_thing(
     _nest_lvl : internal use only. pprint_thing() is mutually-recursive
         with pprint_sequence, this argument is used to keep track of the
         current nesting level, and limit it.
-    escape_chars : list or dict, optional
-        Characters to escape. If a dict is passed the values are the
+    escape_chars : list[str] or Mapping[str, str], optional
+        Characters to escape. If a Mapping is passed the values are the
         replacements
     default_escapes : bool, default False
         Whether the input escape characters replaces or adds to the defaults
@@ -204,11 +204,11 @@ def as_escaped_string(
         thing: Any, escape_chars: EscapeChars | None = escape_chars
     ) -> str:
         translate = {"\t": r"\t", "\n": r"\n", "\r": r"\r"}
-        if isinstance(escape_chars, dict):
+        if isinstance(escape_chars, Mapping):
             if default_escapes:
                 translate.update(escape_chars)
             else:
-                translate = escape_chars
+                translate = escape_chars  # type: ignore[assignment]
             escape_chars = list(escape_chars.keys())
         else:
             escape_chars = escape_chars or ()
@@ -220,7 +220,7 @@ def as_escaped_string(
 
     if hasattr(thing, "__next__"):
         return str(thing)
-    elif isinstance(thing, dict) and _nest_lvl < get_option(
+    elif isinstance(thing, Mapping) and _nest_lvl < get_option(
         "display.pprint_nest_depth"
     ):
         result = _pprint_dict(

pandas/tests/io/formats/test_printing.py

@@ -1,5 +1,6 @@
 # Note! This file is aimed specifically at pandas.io.formats.printing utility
 # functions, not the general printing of pandas objects.
+from collections.abc import Mapping
 import string
 
 import pandas._config.config as cf
@@ -16,6 +17,17 @@ def test_adjoin():
     assert adjoined == expected
 
 
+class MyMapping(Mapping):
+    def __getitem__(self, key):
+        return 4
+
+    def __iter__(self):
+        return iter(["a", "b"])
+
+    def __len__(self):
+        return 2
+
+
 class TestPPrintThing:
     def test_repr_binary_type(self):
         letters = string.ascii_letters
@@ -42,6 +54,12 @@ def test_repr_obeys_max_seq_limit(self):
     def test_repr_set(self):
         assert printing.pprint_thing({1}) == "{1}"
 
+    def test_repr_dict(self):
+        assert printing.pprint_thing({"a": 4, "b": 4}) == "{'a': 4, 'b': 4}"
+
+    def test_repr_mapping(self):
+        assert printing.pprint_thing(MyMapping()) == "{'a': 4, 'b': 4}"
+
 
 class TestFormatBase:
     def test_adjoin(self):