Support square bracket indexing with literal with pinfo/?/pinfo2/??

We add limited support for evaluating `[xxx]` where xxx is a numeric
literal. This still abit dangerous as __getindex__ can run arbitrary
code.

We could support a wider range of constructs, but this would start to
reach into complex and dangerous territory. Alredy this with lead to
weird suff like
   >>> def foo(*arg, **kwargs):pass
   >>> c = [foo]
   >>> c[0]?
   Signature: c[0](*args, **kwargs)

Instead of

   >>> c[0]?
   Signature: foo(*args, **kwargs)

As the name of the object is used in the signature is the one if the
main namespace.

This should fix https://github.com/ipython/ipython/issues/13780

IPython/core/inputtransformer2.py

@@ -429,9 +429,11 b' class EscapedCommand(TokenTransformBase):'
 
         return lines_before + [new_line] + lines_after
 
-_help_end_re = re.compile(r"""(%{0,2}
+
+_help_end_re = re.compile(
+    r"""(%{0,2}
                               (?!\d)[\w*]+            # Variable name
-                              (\.(?!\d)[\w*]+)*       # .etc.etc
+                              (\.(?!\d)[\w*]+|\[[0-9]+\])*       # .etc.etc or [0], we only support literal integers.
                               )
                               (\?\??)$                # ? or ??
                               """,
@@ -464,10 +466,11 b' class HelpEnd(TokenTransformBase):'
     def transform(self, lines):
         """Transform a help command found by the ``find()`` classmethod.
         """
-        piece = ''.join(lines[self.start_line:self.q_line+1])
-        indent, content = piece[:self.start_col], piece[self.start_col:]
-        lines_before = lines[:self.start_line]
-        lines_after = lines[self.q_line + 1:]
+
+        piece = "".join(lines[self.start_line : self.q_line + 1])
+        indent, content = piece[: self.start_col], piece[self.start_col :]
+        lines_before = lines[: self.start_line]
+        lines_after = lines[self.q_line + 1 :]
 
         m = _help_end_re.search(content)
         if not m:
@@ -543,8 +546,13 b' def has_sunken_brackets(tokens: List[tokenize.TokenInfo]):'
 
 def show_linewise_tokens(s: str):
     """For investigation and debugging"""
-    if not s.endswith('\n'):
-        s += '\n'
+    warnings.warn(
+        "show_linewise_tokens is deprecated since IPython 8.6",
+        DeprecationWarning,
+        stacklevel=2,
+    )
+    if not s.endswith("\n"):
+        s += "\n"
     lines = s.splitlines(keepends=True)
     for line in make_tokens_by_line(lines):
         print("Line -------")

IPython/core/interactiveshell.py

@@ -213,14 +213,17 b' class ExecutionInfo(object):'
         raw_cell = (
             (self.raw_cell[:50] + "..") if len(self.raw_cell) > 50 else self.raw_cell
         )
-        return '<%s object at %x, raw_cell="%s" store_history=%s silent=%s shell_futures=%s cell_id=%s>' % (
-            name,
-            id(self),
-            raw_cell,
-            self.store_history,
-            self.silent,
-            self.shell_futures,
-            self.cell_id,
+        return (
+            '<%s object at %x, raw_cell="%s" store_history=%s silent=%s shell_futures=%s cell_id=%s>'
+            % (
+                name,
+                id(self),
+                raw_cell,
+                self.store_history,
+                self.silent,
+                self.shell_futures,
+                self.cell_id,
+            )
         )
 
 
@@ -1537,10 +1540,33 b' class InteractiveShell(SingletonConfigurable):'
         Has special code to detect magic functions.
         """
         oname = oname.strip()
-        if not oname.startswith(ESC_MAGIC) and \
-                not oname.startswith(ESC_MAGIC2) and \
-                not all(a.isidentifier() for a in oname.split(".")):
-            return {'found': False}
+        raw_parts = oname.split(".")
+        parts = []
+        parts_ok = True
+        for p in raw_parts:
+            if p.endswith("]"):
+                var, *indices = p.split("[")
+                if not var.isidentifier():
+                    parts_ok = False
+                    break
+                parts.append(var)
+                for ind in indices:
+                    if ind[-1] != "]" and not ind[:-1].isnumeric():
+                        parts_ok = False
+                        break
+                    parts.append(ind[:-1])
+                continue
+
+            if not p.isidentifier():
+                parts_ok = False
+            parts.append(p)
+
+        if (
+            not oname.startswith(ESC_MAGIC)
+            and not oname.startswith(ESC_MAGIC2)
+            and not parts_ok
+        ):
+            return {"found": False}
 
         if namespaces is None:
             # Namespaces to search in:
@@ -1562,7 +1588,7 b' class InteractiveShell(SingletonConfigurable):'
         # Look for the given name by splitting it in parts.  If the head is
         # found, then we look for all the remaining parts as members, and only
         # declare success if we can find them all.
-        oname_parts = oname.split('.')
+        oname_parts = parts
         oname_head, oname_rest = oname_parts[0],oname_parts[1:]
         for nsname,ns in namespaces:
             try:
@@ -1579,7 +1605,10 b' class InteractiveShell(SingletonConfigurable):'
                         if idx == len(oname_rest) - 1:
                             obj = self._getattr_property(obj, part)
                         else:
-                            obj = getattr(obj, part)
+                            if part.isnumeric():
+                                obj = obj[int(part)]
+                            else:
+                                obj = getattr(obj, part)
                     except:
                         # Blanket except b/c some badly implemented objects
                         # allow __getattr__ to raise exceptions other than
@@ -1643,7 +1672,10 b' class InteractiveShell(SingletonConfigurable):'
                 #
                 # The universal alternative is to traverse the mro manually
                 # searching for attrname in class dicts.
-                attr = getattr(type(obj), attrname)
+                if attrname.isnumeric():
+                    return obj[int(attrname)]
+                else:
+                    attr = getattr(type(obj), attrname)
             except AttributeError:
                 pass
             else:

IPython/core/tests/test_oinspect.py

@@ -5,6 +5,7 b''
 # Distributed under the terms of the Modified BSD License.
 
 
+from contextlib import contextmanager
 from inspect import signature, Signature, Parameter
 import inspect
 import os
@@ -43,7 +44,7 b' class SourceModuleMainTest:'
 # defined, if any code is inserted above, the following line will need to be
 # updated.  Do NOT insert any whitespace between the next line and the function
 # definition below.
-THIS_LINE_NUMBER = 46  # Put here the actual number of this line
+THIS_LINE_NUMBER = 47  # Put here the actual number of this line
 
 
 def test_find_source_lines():
@@ -345,6 +346,56 b' def test_pdef():'
     inspector.pdef(foo, 'foo')
 
 
+@contextmanager
+def cleanup_user_ns(**kwargs):
+    """
+    On exit delete all the keys that were not in user_ns before entering.
+
+    It does not restore old values !
+
+    Parameters
+    ----------
+
+    **kwargs
+        used to update ip.user_ns
+
+    """
+    try:
+        known = set(ip.user_ns.keys())
+        ip.user_ns.update(kwargs)
+        yield
+    finally:
+        added = set(ip.user_ns.keys()) - known
+        for k in added:
+            del ip.user_ns[k]
+
+
+def test_pinfo_getindex():
+    def dummy():
+        """
+        MARKER
+        """
+
+    container = [dummy]
+    with cleanup_user_ns(container=container):
+        with AssertPrints("MARKER"):
+            ip._inspect("pinfo", "container[0]", detail_level=0)
+    assert "container" not in ip.user_ns.keys()
+
+
+def test_qmark_getindex():
+    def dummy():
+        """
+        MARKER 2
+        """
+
+    container = [dummy]
+    with cleanup_user_ns(container=container):
+        with AssertPrints("MARKER 2"):
+            ip.run_cell("container[0]?")
+    assert "container" not in ip.user_ns.keys()
+
+
 def test_pinfo_nonascii():
     # See gh-1177
     from . import nonascii2

IPython/testing/plugin/pytest_ipdoctest.py

@@ -782,7 +782,7 b' def _init_checker_class() -> Type["IPDoctestOutputChecker"]:'
                 precision = 0 if fraction is None else len(fraction)
                 if exponent is not None:
                     precision -= int(exponent)
-                if float(w.group()) == approx(float(g.group()), abs=10 ** -precision):
+                if float(w.group()) == approx(float(g.group()), abs=10**-precision):
                     # They're close enough. Replace the text we actually
                     # got with the text we want, so that it will match when we
                     # check the string literally.