# Expr

> **Class** in `langchain_core`

📖 [View in docs](https://reference.langchain.com/python/langchain-core/structured_query/Expr)

Base class for all expressions.

## Signature

```python
Expr()
```

## Extends

- `BaseModel`

## Methods

- [`accept()`](https://reference.langchain.com/python/langchain-core/structured_query/Expr/accept)

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[View source on GitHub](https://github.com/langchain-ai/langchain/blob/9f232caa7a8fe1ca042a401942d5d90d54ceb1a6/libs/core/langchain_core/structured_query.py#L82)