Implementation:Evidentlyai Evidently Legacy Text Part Feature

Knowledge Sources	Evidentlyai_Evidently
Domains	NLP, Feature Engineering, Text Analysis
Last Updated	2026-02-14 12:00 GMT

Overview

This module provides two generated feature classes -- BeginsWith and EndsWith -- for checking whether text values in a column start or end with a specified substring.

Description

Both classes extend GeneratedFeature and produce ColumnType.Categorical (boolean) outputs.

BeginsWith checks whether each text value in the specified column starts with a given prefix. EndsWith checks whether each text value ends with a given suffix. Both support an optional case_sensitive flag; when set to False, both the column data and the substring are case-folded before comparison using Python's str.casefold() method.

The feature column names are constructed as {column_name}.{prefix/suffix}.{case_sensitive}, and the display names follow the patterns "Text Begins with [{prefix}] for {column_name}" and "Text Ends with [{suffix}] for {column_name}" respectively.

Usage

Use these features when you need to identify or filter text entries based on their prefixes or suffixes. Common use cases include verifying that generated text follows expected formatting patterns, detecting specific greeting phrases, or checking for particular file extensions or URL patterns in text data.

Code Reference

Source Location

Repository: Evidentlyai_Evidently
File: src/evidently/legacy/features/text_part_feature.py

Signature

class BeginsWith(GeneratedFeature):
    class Config:
        type_alias = "evidently:feature:BeginsWith"
    __feature_type__: ClassVar = ColumnType.Categorical
    column_name: str
    case_sensitive: bool
    prefix: str
    def __init__(self, column_name: str, prefix: str, case_sensitive: bool = True,
                 display_name: Optional[str] = None): ...
    def generate_feature(self, data: pd.DataFrame, data_definition: DataDefinition) -> pd.DataFrame: ...

class EndsWith(GeneratedFeature):
    class Config:
        type_alias = "evidently:feature:EndsWith"
    __feature_type__: ClassVar = ColumnType.Categorical
    column_name: str
    case_sensitive: bool
    suffix: str
    def __init__(self, column_name: str, suffix: str, case_sensitive: bool = True,
                 display_name: Optional[str] = None): ...
    def generate_feature(self, data: pd.DataFrame, data_definition: DataDefinition) -> pd.DataFrame: ...

Import

from evidently.legacy.features.text_part_feature import BeginsWith
from evidently.legacy.features.text_part_feature import EndsWith

I/O Contract

Inputs (BeginsWith)

Name	Type	Required	Description
column_name	str	Yes	Name of the text column to check
prefix	str	Yes	The prefix string to check for at the beginning of text values
case_sensitive	bool	No	Whether matching is case-sensitive (default: True)
display_name	Optional[str]	No	Custom display name for the generated feature column

Inputs (EndsWith)

Name	Type	Required	Description
column_name	str	Yes	Name of the text column to check
suffix	str	Yes	The suffix string to check for at the end of text values
case_sensitive	bool	No	Whether matching is case-sensitive (default: True)
display_name	Optional[str]	No	Custom display name for the generated feature column

Outputs

Name	Type	Description
generated feature column	bool	True if the text starts with (or ends with) the specified substring, False otherwise

Usage Examples

from evidently.legacy.features.text_part_feature import BeginsWith, EndsWith

# Check if responses begin with a greeting
begins_feature = BeginsWith(
    column_name="response",
    prefix="Hello",
    case_sensitive=False
)

# Check if URLs end with a specific extension
ends_feature = EndsWith(
    column_name="url",
    suffix=".html",
    case_sensitive=True
)

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