Expr.List (ListOps)

Namespace: Polars.FSharp

Instance Methods

Agg

Run any polars aggregation expression against the list’ elements.

fsharp

member Agg(expr: Expr) : Expr

Parameters

Name	Type	Description
`expr`	`Expr`	Expression to run. Note that you can select an element with Pl.Element().

All

Evaluate whether all boolean values in a list are true.

fsharp

member All(?ignoreNulls: bool) : Expr

Parameters

Name	Type	Description
`ignoreNulls`	`bool (optional)`	-

Any

Evaluate whether any boolean value in a list is true.

fsharp

member Any(?ignoreNulls: bool) : Expr

Parameters

Name	Type	Description
`ignoreNulls`	`bool (optional)`	-

ArgMax

Retrieve the index of the maximum value in every sublist.

fsharp

member ArgMax : unit -> Expr

ArgMin

Retrieve the index of the minimum value in every sublist.

fsharp

member ArgMin : unit -> Expr

Concat

Combine the current expression with other expressions into a List. Result: [parent_val, other_val_1, other_val_2, ...] Equivalent to: pl.concatList([parent, others...])

Overload: Concat a single expression/column.

fsharp

member Concat(others: seq<'b>) : Expr
member Concat(other: 'a) : Expr

Parameters

Name	Type	Description
`others`	`seq<'b>`	-
`other`	`'a`	-

Contains

Check if the list contains the given item.

fsharp

member Contains(item: Expr, ?nullsEqual: bool) : Expr
member Contains(item: int, ?nullsEqual: bool) : Expr
member Contains(item: string, ?nullsEqual: bool) : Expr

Parameters

Name	Type	Description
`item`	`Expr / int / string`	-
`nullsEqual`	`bool (optional)`	-

Diff

Calculate the first discrete difference between shifted items of every sublist.

fsharp

member Diff(?n: int64, ?nullBehavior: NullBehavior) : Expr

Parameters

Name	Type	Description
`n`	`int64 (optional)`	Number of slots to shift.
`nullBehavior`	`NullBehavior (optional)`	How to handle null values.

DropNulls

Drop all null values in the list. The original order of the remaining elements is preserved.

fsharp

member DropNulls : unit -> Expr

Eval

Run any polars expression against the lists’ elements.

fsharp

member Eval(expr: Expr) : Expr

Parameters

Name	Type	Description
`expr`	`Expr`	Expression to run. Note that you can select an element with Pl.Element().

Explode

Explode a list expression.

This turns a list column into a long column (flattening).

Warning: When used in DataFrame.Select with other columns, it may cause a length mismatch error if the other columns are not broadcasted. Use DataFrame.Explode for safely exploding columns while repeating others.

fsharp

member Explode(?emptyAsNull: bool, ?keepNulls: bool) : Expr

Parameters

Name	Type	Description
`emptyAsNull`	`bool (optional)`	-
`keepNulls`	`bool (optional)`	-

First

Get the first element of the list.

fsharp

member First : unit -> Expr

Gather

Take sublists by multiple indices.The indices may be defined in a single column, or by sublists in another column of dtype List.

fsharp

member Gather(indices: Expr, ?nullOnOob: bool) : Expr

Parameters

Name	Type	Description
`indices`	`Expr`	Indices to return per sublist
`nullOnOob`	`bool (optional)`	Behavior if an index is out of bounds: True -> set as null False -> raise an error Note that defaulting to raising an error is much cheaper

GatherEvery

Take every n-th value start from offset in sublists.

fsharp

member GatherEvery(n: Expr, ?offset: Expr) : Expr

Parameters

Name	Type	Description
`n`	`Expr`	Gather every n-th element.
`offset`	`Expr (optional)`	Starting Index

Get

Get element at index.

fsharp

member Get(index: int, ?nullOnOob: bool) : Expr

Parameters

Name	Type	Description
`index`	`int`	-
`nullOnOob`	`bool (optional)`	-

Head

Slice the first n values of every sublist.

fsharp

member Head(?n: Expr) : Expr

Parameters

Name	Type	Description
`n`	`Expr (optional)`	Number of values to return for each sublist.

Join

Join list elements with separator.

fsharp

member Join(separator: string, ?ignoreNulls: bool) : Expr

Parameters

Name	Type	Description
`separator`	`string`	-
`ignoreNulls`	`bool (optional)`	-

Last

Get the Last element of the list.

fsharp

member Last : unit -> Expr

Len

Return the number of elements in each list.

fsharp

member Len : unit -> Expr

Max

Calculate the max of the list elements.

fsharp

member Max : unit -> Expr

Mean

Calculate the mean of the list elements.

fsharp

member Mean : unit -> Expr

Median

Calculate the median of the list elements.

fsharp

member Median : unit -> Expr

Min

Calculate the min of the list elements.

fsharp

member Min : unit -> Expr

NUnique

Count the number of unique values in every sub-lists.

fsharp

member NUnique : unit -> Expr

Reverse

Reverse the list.

fsharp

member Reverse : unit -> Expr

SampleFrac

Sample from this list.

fsharp

member SampleFrac(
    fraction: Expr,
    ?withReplacement: bool,
    ?shuffle: bool,
    ?seed: uint64
) : Expr

Parameters

Name	Type	Description
`fraction`	`Expr`	Fraction of items to return.
`withReplacement`	`bool (optional)`	Allow values to be sampled more than once.
`shuffle`	`bool (optional)`	Shuffle the order of sampled data points.
`seed`	`uint64 (optional)`	Seed for the random number generator. If set to None (default), a random seed is generated for each sample operation.

SampleN

Sample from this list.

fsharp

member SampleN(
    ?n: Expr,
    ?withReplacement: bool,
    ?shuffle: bool,
    ?seed: uint64
) : Expr

Parameters

Name	Type	Description
`n`	`Expr (optional)`	Number of items to return.Defaults to 1
`withReplacement`	`bool (optional)`	Allow values to be sampled more than once.
`shuffle`	`bool (optional)`	Shuffle the order of sampled data points.
`seed`	`uint64 (optional)`	Seed for the random number generator. If set to None (default), a random seed is generated for each sample operation.

SetDifference

Compute the SET DIFFERENCE between the elements in this list and the elements of other.

fsharp

member SetDifference(other: Expr) : Expr

Parameters

Name	Type	Description
`other`	`Expr`	Right hand side of the set operation.

SetIntersection

Compute the SET INTERSECTION between the elements in this list and the elements of other.

fsharp

member SetIntersection(other: Expr) : Expr

Parameters

Name	Type	Description
`other`	`Expr`	Right hand side of the set operation.

SetSymmetricDifference

Compute the SET SYMMETRIC DIFFERENCE between the elements in this list and the elements of other.

fsharp

member SetSymmetricDifference(other: Expr) : Expr

Parameters

Name	Type	Description
`other`	`Expr`	Right hand side of the set operation.

SetUnion

Compute the SET UNION between the elements in this list and the elements of other.

fsharp

member SetUnion(other: Expr) : Expr

Parameters

Name	Type	Description
`other`	`Expr`	Right hand side of the set operation.

Shift

Shift list values by the given number of indices.

fsharp

member Shift(?n: Expr) : Expr

Parameters

Name	Type	Description
`n`	`Expr (optional)`	Number of indices to shift forward. If a negative value is passed, values are shifted in the opposite direction instead.

Slice

Slice every sublist.

fsharp

member Slice(offset: Expr, ?length: Expr) : Expr

Parameters

Name	Type	Description
`offset`	`Expr`	Start index. Negative indexing is supported.
`length`	`Expr (optional)`	Length of the slice. If null, the slice is taken to the end of the list.

Sort

Sort the lists in this column.

fsharp

member Sort(?descending: bool, ?nullsLast: bool, ?maintainOrder: bool) : Expr

Parameters

Name	Type	Description
`descending`	`bool (optional)`	Sort in descending order.
`nullsLast`	`bool (optional)`	Place null values last.
`maintainOrder`	`bool (optional)`	-

Std

Get the standard deviation.

fsharp

member Std(?ddof: byte) : Expr

Parameters

Name	Type	Description
`ddof`	`byte (optional)`	“Delta Degrees of Freedom”: the divisor used in the calculation is N - ddof, where N represents the number of elements. By default ddof is 1.

Sum

Calculate the sum of the values in the list (row-wise).

fsharp

member Sum : unit -> Expr

Tail

Slice the last n values of every sublist.

fsharp

member Tail(?n: Expr) : Expr

Parameters

Name	Type	Description
`n`	`Expr (optional)`	Number of values to return for each sublist.

ToArray

Convert a List column into an Array column with the same inner data type.

fsharp

member ToArray(width: int64) : Expr

Parameters

Name	Type	Description
`width`	`int64`	Width of the resulting Array column.

ToStruct

Convert the list to a struct type with explicitly named fields.

Convert the list to a struct type using a function to generate field names.

Convert the list to a struct type up to a maximum number of fields, using default naming ("field_0", "field_1", ...).

fsharp

member ToStruct(fields: seq<string>) : Expr
member ToStruct(nameGenerator: (int -> string), fieldCount: int) : Expr
member ToStruct(upperBound: int) : Expr

Parameters

Name	Type	Description
`fields`	`seq<string>`	A sequence of names for the struct fields.
`nameGenerator`	`(int -> string)`	A function that takes a field index and returns the field name.
`fieldCount`	`int`	The number of struct fields to create.
`upperBound`	`int`	The maximum number of struct fields to create. Used for compile-time schema inference.

Returns: A new Expr representing the struct conversion.

Unique

Get the unique/distinct values in the list.

fsharp

member Unique(?maintainOrder: bool) : Expr

Parameters

Name	Type	Description
`maintainOrder`	`bool (optional)`	Maintain order of data. This requires more work.

Var

Get the variance.

fsharp

member Var(?ddof: byte) : Expr

Parameters

Name	Type	Description
`ddof`	`byte (optional)`	“Delta Degrees of Freedom”: the divisor used in the calculation is N - ddof, where N represents the number of elements. By default ddof is 1.

Expr.List (ListOps) ​

Instance Methods ​

Agg ​

All ​

Any ​

ArgMax ​

ArgMin ​

Concat ​

Contains ​

Diff ​

DropNulls ​

Eval ​

Explode ​

First ​

Gather ​

GatherEvery ​

Get ​

Head ​

Join ​

Last ​

Len ​

Max ​

Mean ​

Median ​

Min ​

NUnique ​

Reverse ​

SampleFrac ​

SampleN ​

SetDifference ​

SetIntersection ​

SetSymmetricDifference ​

SetUnion ​

Shift ​

Slice ​

Sort ​

Std ​

Sum ​

Tail ​

ToArray ​

ToStruct ​

Unique ​

Var ​

Expr.List (ListOps)

Instance Methods

Agg

All

Any

ArgMax

ArgMin

Concat

Contains

Diff

DropNulls

Eval

Explode

First

Gather

GatherEvery

Get

Head

Join

Last

Len

Max

Mean

Median

Min

NUnique

Reverse

SampleFrac

SampleN

SetDifference

SetIntersection

SetSymmetricDifference

SetUnion

Shift

Slice

Sort

Std

Sum

Tail

ToArray

ToStruct

Unique

Var