Polars.Selectors

Namespace: Polars.CSharp

String matching selectors namespace. Usage: Cs.StartsWith("A") or Pl.Cs.StartWith("A")

Constructors & Static Methods

All

Select all columns.

public static Selector All()

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Alpha

Select all columns with alphabetic names.

public static Selector Alpha(bool asciiOnly = false, bool ignoreSpaces = false)

Parameters

Name	Type	Description
asciiOnly	bool	-
ignoreSpaces	bool	-

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Alphanumeric

Select all columns with alphanumeric names.

public static Selector Alphanumeric(bool asciiOnly = false, bool ignoreSpaces = false)

Parameters

Name	Type	Description
asciiOnly	bool	-
ignoreSpaces	bool	-

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Array

Select array columns. Optionally filter by inner data type and fixed width.

public static Selector Array(Selector? inner = null, long? width = null)

Parameters

Name	Type	Description
inner	Selector?	-
width	long?	-

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Binary

public static Selector Binary()

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Boolean

public static Selector Boolean()

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ByDtype

Select columns by specific DataType.

Select columns by Generic Type.

public static Selector ByDtype(DataType type)
public static Selector ByDtype(Type type)
public static Selector ByDtype<T>()

Parameters

Name	Type	Description
type	DataType	-

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ByIndex

Select columns by their index. Usage: Cs.ByIndex(0, 2, 4)

Select columns by their index with strictness control.

public static Selector ByIndex(ReadOnlySpan<long> indices)
public static Selector ByIndex(ReadOnlySpan<long> indices, bool strict)

Parameters

Name	Type	Description
indices	ReadOnlySpan<long>	-
strict	bool	-

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ByName

Select columns.

public static Selector ByName(params string[] columns)

Parameters

Name	Type	Description
columns	string[]	-

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CJK

[EN] Select columns whose names consist entirely of CJK scripts (Han, Hiragana, Katakana, Hangul). The 'chinese' option enables \p{Han}, which also includes Japanese Kanji and Korean Hanja.

[ZH] 选择列名完全由中日韩字符（Han / 平假名 / 片假名 / 韩文）组成的列。 注意：'chinese' 实际匹配 \p{Han}，包含日文汉字与韩文汉字。

[JA] 列名がCJK文字（漢字・ひらがな・カタカナ・ハングル）のみで構成される列を選択します。 ※ 'chinese' は \p{Han}（日本・韓国の漢字を含む）を有効にします。

[KO] 열 이름이 CJK 문자(한자, 히라가나, 가타카나, 한글)로만 구성된 열을 선택합니다. ※ 'chinese'는 \p{Han}을 의미하며 일본/한국 한자도 포함합니다.

public static Selector CJK(
    bool chinese = true,
    bool japanese = true,
    bool korean = true,
    bool ignoreSpaces = false
)

Parameters

Name	Type	Description
chinese	bool	-
japanese	bool	-
korean	bool	-
ignoreSpaces	bool	-

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CJKAlphanumeric

[EN] Select columns whose names consist of CJK scripts, Unicode digits (\p{N}), and optionally ASCII/full-width Latin letters.

[ZH] 选择列名由中日韩字符、数字（\p{N}，含全/半角）以及可选英文字母（全/半角）组成的列。

[JA] 列名がCJK文字・数字（\p{N}、全角/半角）および英字（全角/半角）で構成される列を選択します。

[KO] 열 이름이 CJK 문자, 숫자(\p{N}, 전각/반각) 및 영문자(전각/반각)로 구성된 열을 선택합니다.

public static Selector CJKAlphanumeric(
    bool chinese = true,
    bool japanese = true,
    bool korean = true,
    bool includeLetters = true,
    bool ignoreSpaces = false
)

Parameters

Name	Type	Description
chinese	bool	-
japanese	bool	-
korean	bool	-
includeLetters	bool	-
ignoreSpaces	bool	-

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Contains

Select column whose name contains given string.

public static Selector Contains(string str)

Parameters

Name	Type	Description
str	string	-

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Date

Select all date columns.

public static Selector Date()

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Datetime

Select all datetime columns (both with and without timezones).

public static Selector Datetime(TimeUnit? timeUnit = null)

Parameters

Name	Type	Description
timeUnit	TimeUnit?	-

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DatetimeAware

Select ONLY timezone-aware datetime columns (any timezone).

public static Selector DatetimeAware(TimeUnit? timeUnit = null)

Parameters

Name	Type	Description
timeUnit	TimeUnit?	-

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DatetimeExact

Select datetime columns matching a specific timezone (e.g., "UTC", "Asia/Shanghai").

public static Selector DatetimeExact(string timeZone, TimeUnit? timeUnit = null)

Parameters

Name	Type	Description
timeZone	string	-
timeUnit	TimeUnit?	-

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DatetimeNaive

Select ONLY timezone-naive datetime columns (no timezone set).

public static Selector DatetimeNaive(TimeUnit? timeUnit = null)

Parameters

Name	Type	Description
timeUnit	TimeUnit?	-

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Decimal

public static Selector Decimal()

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Duration

Select all duration columns. Optionally match a specific TimeUnit.

public static Selector Duration(TimeUnit? timeUnit = null)

Parameters

Name	Type	Description
timeUnit	TimeUnit?	-

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Empty

public static Selector Empty()

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EndsWith

Select column whose name ends with given suffix.

public static Selector EndsWith(string suffix)

Parameters

Name	Type	Description
suffix	string	-

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Enum

public static Selector Enum()

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Exclude

Select all columns EXCEPT the specified Selectors.

Select all columns EXCEPT the specified Data Types.

Select all columns EXCEPT the specified Column names.

public static Selector Exclude(ReadOnlySpan<Selector> selectors)
public static Selector Exclude(ReadOnlySpan<DataType> dtypes)
public static Selector Exclude(params string[] columns)

Parameters

Name	Type	Description
selectors	ReadOnlySpan<Selector>	-
dtypes	ReadOnlySpan<DataType>	-
columns	string[]	-

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ExpandSelector

Expand a Selector against a DataFrame to get the matched column names.

Expand an Expr against a DataFrame to get the matched column names.

public static string[] ExpandSelector(DataFrame target, Selector selector)
public static string[] ExpandSelector(DataFrame target, Expr expr)
public static string[] ExpandSelector(LazyFrame target, Selector selector)

Parameters

Name	Type	Description
target	DataFrame / LazyFrame	-
selector	Selector	-
expr	Expr	-

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First

Select the first column.

public static Selector First()

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Float

public static Selector Float()

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Integer

public static Selector Integer()

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Last

Select the last column.

public static Selector Last()

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List

Select list columns. Optionally filter by the inner data type. Example: Cs.List(Cs.Integer())

public static Selector List(Selector? inner = null)

Parameters

Name	Type	Description
inner	Selector?	-

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Matches

Select column whose name matches given string.

public static Selector Matches(string regex)

Parameters

Name	Type	Description
regex	string	Regular Expression

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Nested

public static Selector Nested()

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Numeric

Select all numeric columns (Int, Float, etc.).

public static Selector Numeric()

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SignedInteger

public static Selector SignedInteger()

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StartsWith

Select column whose name starts with given prefix.

public static Selector StartsWith(string prefix)

Parameters

Name	Type	Description
prefix	string	-

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String

Select all string/utf8 columns.

public static Selector String()

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Struct

public static Selector Struct()

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Temporal

public static Selector Temporal()

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UnsignedInteger

public static Selector UnsignedInteger()

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