==== Meta

The following methods are available under the expr.meta attribute.

These operations allow you to modify the expressions or check for equality of the expressions themselves instead of answering questions on the data.

This can for instance be useful to create a set of unique expressions.

.. code-block:: python

   a1 = pl.col("a")
   a2 = pl.col("a")
   b1 = pl.col("b") + 1
   b2 = pl.col("b") + 2
   b3 = pl.col("b") + 2

   # Create a set of meta expressions to deduplicate
   s = {e.meta for e in [a1, a2, b1, b2, b3]}
   assert len(s) == 3

   # Turn back into expressions to get the final unique expressions
   unique_expressions = [e.as_expression() for e in s]

.. currentmodule:: polars .. autosummary:: :toctree: api/ :template: autosummary/accessor_method.rst

Expr.meta.as_expression
Expr.meta.eq
Expr.meta.has_multiple_outputs
Expr.meta.is_column
Expr.meta.is_column_selection
Expr.meta.is_literal
Expr.meta.is_regex_projection
Expr.meta.ne
Expr.meta.output_name
Expr.meta.pop
Expr.meta.root_names
Expr.meta.serialize
Expr.meta.show_graph
Expr.meta.tree_format
Expr.meta.undo_aliases
Expr.meta.write_json