pandas-dev/pandas · error · ValueError

cannot subscript {value!r} with {slobj!r}

Error message

cannot subscript {value!r} with {slobj!r}

What it means

Raised by PyTablesExprVisitor.visit_Subscript in pandas.core.computation.pytables when subscripting a value in a where clause raises TypeError. The visitor resolves node.value and node.slice, attempts value[slobj], and on TypeError re-raises as ValueError with both the value and the subscript object. Only simple subscripts are supported (e.g. df.index[3]); anything more elaborate (multi-axis, non-integer keys, unsupported types) trips this.

Source

Thrown at pandas/core/computation/pytables.py:496

    def visit_Subscript(self, node, **kwargs) -> ops.Term:
        # only allow simple subscripts

        value = self.visit(node.value)
        slobj = self.visit(node.slice)
        try:
            value = value.value
        except AttributeError:
            pass

        if isinstance(slobj, Term):
            # In py39 np.ndarray lookups with Term containing int raise
            slobj = slobj.value

        try:
            return self.const_type(value[slobj], self.env)
        except TypeError as err:
            raise ValueError(f"cannot subscript {value!r} with {slobj!r}") from err

    def visit_Attribute(self, node, **kwargs):
        attr = node.attr
        value = node.value

        ctx = type(node.ctx)
        if ctx == ast.Load:
            # resolve the value
            resolved = self.visit(value)

            # try to get the value to see if we are another expression
            try:
                resolved = resolved.value
            except AttributeError:
                pass

            try:
                return self.term_type(getattr(resolved, attr), self.env)

View on GitHub (pinned to 71959b8cb9)

Solutions

1. Resolve the subscript in Python first and pass the resulting scalar: idx = df.index[3]; store.select('df', where=f'index == {idx!r}').
2. Restrict subscripts to simple integer indexing of an existing index/Series.
3. If you need dict/list lookups, precompute them into a column and query that column.
4. Inspect the types: print(repr(value), repr(slobj)) to find what is not subscriptable.

Example fix

# before
store.select('df', where='index[df] > 5')  # ValueError: cannot subscript ...

# after (precompute the key)
target = df.index[3]
store.select('df', where=f'index == {target!r}')

def precompute_subscript(where: str, df):
    import re
    # resolve simple df.index[N] -> literal value
    def repl(m):
        target, idx = m.group(1), int(m.group(2))
        return repr(getattr(df, target)[idx])
    return re.sub(r'(\w+)\[(\d+)\]', repl, where)

try:
    store.select('df', where=where)
except ValueError as e:
    if 'cannot subscript' in str(e):
        # precompute subscripts to literals and retry
        where = precompute_subscript(where, df)
        store.select('df', where=where)
    else:
        raise

When it happens

Trigger: store.select('df', where='index[df] == 5') (subscripting with a non-int); where='a["foo"] == 1' (string subscript on a non-string-indexable value); where='x[1,2] == 0' (multi-axis subscript); using a column name as the subscript target that doesn't support __getitem__ with the given key.

Common situations: Referencing nested data structures or attempting list/dict subscript semantics inside a where string; assuming arbitrary Python subscript syntax works in pytables expressions.

Related errors

• name {self.name!r} is not defined
• arithmetic operations are not supported inside an HDFStore '
• Cannot compare {conv_val} of type {type(conv_val)} to {kind}
• query term is not valid [{self}]
• passing a filterable condition to a non-table indexer [{self

AI-assisted analysis of pandas-dev/pandas@71959b8cb9 (2026-08-07). Data as JSON: /api/errors/d68346af43775a97. Report an issue: GitHub.