support negative indexing

IPython/core/inputtransformer2.py

@@ -432,12 +432,14 b' class EscapedCommand(TokenTransformBase):'
 
 _help_end_re = re.compile(
     r"""(%{0,2}
-                              (?!\d)[\w*]+            # Variable name
-                              (\.(?!\d)[\w*]+|\[[0-9]+\])*       # .etc.etc or [0], we only support literal integers.
-                              )
-                              (\?\??)$                # ? or ??
-                              """,
-                              re.VERBOSE)
+    (?!\d)[\w*]+            # Variable name
+    (\.(?!\d)[\w*]+|\[-?[0-9]+\])*       # .etc.etc or [0], we only support literal integers.
+    )
+    (\?\??)$                # ? or ??
+    """,
+    re.VERBOSE,
+)
+
 
 class HelpEnd(TokenTransformBase):
     """Transformer for help syntax: obj? and obj??"""

IPython/core/interactiveshell.py

@@ -147,6 +147,17 b" dedent_re = re.compile(r'^\\s+raise|^\\s+return|^\\s+pass')"
 # Utilities
 #-----------------------------------------------------------------------------
 
+def is_integer_string(s:str):
+    """
+    Variant of "str.isnumeric()" that allow negative values and other ints.
+    """
+    try:
+        int(s)
+        return True
+    except ValueError:
+        return False
+    raise ValueError('Unexpected error')
+
 @undoc
 def softspace(file, newvalue):
     """Copied from code.py, to remove the dependency"""
@@ -1548,7 +1559,7 b' class InteractiveShell(SingletonConfigurable):'
                     break
                 parts.append(var)
                 for ind in indices:
-                    if ind[-1] != "]" and not ind[:-1].isnumeric():
+                    if ind[-1] != "]" and not is_integer_string(ind[:-1]):
                         parts_ok = False
                         break
                     parts.append(ind[:-1])
@@ -1602,7 +1613,7 b' class InteractiveShell(SingletonConfigurable):'
                         if idx == len(oname_rest) - 1:
                             obj = self._getattr_property(obj, part)
                         else:
-                            if part.isnumeric():
+                            if is_integer_string(part):
                                 obj = obj[int(part)]
                             else:
                                 obj = getattr(obj, part)
@@ -1669,7 +1680,7 b' class InteractiveShell(SingletonConfigurable):'
                 #
                 # The universal alternative is to traverse the mro manually
                 # searching for attrname in class dicts.
-                if attrname.isnumeric():
+                if is_integer_string(attrname):
                     return obj[int(attrname)]
                 else:
                     attr = getattr(type(obj), attrname)

IPython/core/tests/test_oinspect.py

@@ -395,6 +395,19 b' def test_qmark_getindex():'
             ip.run_cell("container[0]?")
     assert "container" not in ip.user_ns.keys()
 
+def test_qmark_getindex_negatif():
+    def dummy():
+        """
+        MARKER 3
+        """
+
+    container = [dummy]
+    with cleanup_user_ns(container=container):
+        with AssertPrints("MARKER 3"):
+            ip.run_cell("container[-1]?")
+    assert "container" not in ip.user_ns.keys()
+
+
 
 def test_pinfo_nonascii():
     # See gh-1177