pathwaycom/pathway · error · TypeError

Pathway does not support using binary operator {operator.__n

Error message

Pathway does not support using binary operator {operator.__name__} on columns of types {original_left.typehint}, {original_right.typehint}.\nIt refers to the following expression:\n{expression_info}

What it means

Raised by the type interpreter when a binary operator (e.g. +, *, ==, &) is applied to column types for which Pathway defines no combined operation. The interpreter checks the left/right dtypes (including tuple/list element-wise rules); on failure it reports the operator, both original typehints, and the expression trace so the offending line can be located.

Source

Thrown at python/pathway/internals/type_interpreter.py:151

            return dtype

        left_dtype, right_dtype = dt.unoptionalize_pair(left_dtype, right_dtype)

        if (
            dtype_and_handler := get_binary_operators_mapping_optionals(
                operator, left_dtype, right_dtype
            )
        ) is not None:
            return dtype_and_handler[0]

        maybe_dtype = self._eval_binary_op_on_tuples(
            left_dtype, right_dtype, operator, expression
        )
        if maybe_dtype is not None:
            return maybe_dtype

        expression_info = get_expression_info(expression)
        raise TypeError(
            f"Pathway does not support using binary operator {operator.__name__}"
            + f" on columns of types {original_left.typehint}, {original_right.typehint}.\n"
            + "It refers to the following expression:\n"
            + expression_info
        )

    def _eval_binary_op_on_tuples(
        self,
        left_dtype: dt.DType,
        right_dtype: dt.DType,
        operator: Any,
        expression: expr.ColumnExpression,
    ) -> dt.DType | None:
        if (
            isinstance(left_dtype, (dt.Tuple, dt.List))
            and isinstance(right_dtype, (dt.Tuple, dt.List))
            and operator in tuple_handling_operators
        ):

View on GitHub (pinned to fa2f74a464)

Solutions

1. Cast the operands to compatible types before the operation: pw.this.col.astype(float) + pw.this.other.astype(float)
2. Ensure connector dtypes are correct: declare proper types in the input Schema (int, float) instead of relying on inferred str
3. For Optional columns, apply unwrap or replace None defaults first so both sides have concrete dtypes
4. If the mix is intentional, cast both sides to Any (pw.cast_to(Any)) to defer typing — last resort as it removes safety

Example fix

# before
result = table.select(total=pw.this.price * pw.this.amount)  # str * int unsupported

# after
result = table.select(total=pw.this.price.astype(float) * pw.this.amount.astype(int))

import pathway as pw

def dtypes_compatible(l, r) -> bool:
    """Cheap check: both numeric, both str, or equal types."""
    num = lambda t: t in (pw.typehints.Int(), pw.typehints.Float())
    return (num(l) and num(r)) or l.equivalent_to(r)

def both_numeric(l, r) -> bool:
    import pathway as pw
    num = lambda t: t in (pw.typehints.Int(), pw.typehints.Float())
    return num(l) and num(r)

try:
    out = t.select(v=pw.this.a * pw.this.b)
except TypeError:
    out = t.select(v=pw.this.a.astype(float) * pw.this.b.astype(float))

When it happens

Trigger: pw.this.quantity * pw.this.label where one is int and the other str; comparing incompatible types like pw.this.date_col == pw.this.id with mixed types; arithmetic between str and int columns; mixing bool with int under operators Pathway does not map for that pair.

Common situations: CSV/JSON ingestion where everything arrives as str or Any and users do arithmetic immediately; comparing a DateTime column to a plain str literal; Optional columns combined with plain columns without unwrapping; pandas-to-Pathway ports relying on implicit coercion.

Related errors

• Pathway does not support using unary operator {operator_fun.
• Cannot change type from {right} to {left}.\npw.`declare_type
• Incompatible types in for a coalesce expression.\nThe types
• Cannot perform pathway.if_else on columns of types {then_dty
• Pathway does not support using binary operator {expression._

AI-assisted analysis of pathwaycom/pathway@fa2f74a464 (2026-08-15). Data as JSON: /api/errors/7f7e004c6f4d9a11. Report an issue: GitHub.