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  * [ __ ](../../../index.html)
  * [ Python API reference ](../../index.html)
  * __
  * [ Manipulation/selection ](../modify_select.html)
  * polars.LazyF... 

#  polars.LazyFrame.group_by  #

LazyFrame.  group_by  (

     _ *  by  :  IntoExpr  |  Iterable  [  IntoExpr  ]  _ , 
     _ maintain_order  :  [ bool  ](https://docs.python.org/3/library/functions.html#bool "\(in Python v3.12\)") =  False  _ , 
     _ **  named_by  :  IntoExpr  _ , 
)  →  LazyGroupBy  [ [source]  ](https://github.com/pola-
rs/polars/blob/main/py-polars/polars/lazyframe/frame.py#L3001-L3098) #

    

Start a group by operation.

Parameters  :

    

***by**

    

Column(s) to group by. Accepts expression input. Strings are parsed as column
names.

**maintain_order**

    

Ensure that the order of the groups is consistent with the input data. This is
slower than a default group by. Setting this to ` True  ` blocks the
possibility to run on the streaming engine.

****named_by**

    

Additional columns to group by, specified as keyword arguments. The columns
will be renamed to the keyword used.

Examples

Group by one column and call ` agg  ` to compute the grouped sum of another
column.

    
    
    >>> lf = pl.LazyFrame(
    ...     {
    ...         "a": ["a", "b", "a", "b", "c"],
    ...         "b": [1, 2, 1, 3, 3],
    ...         "c": [5, 4, 3, 2, 1],
    ...