Implementation:Eventual Inc Daft DataFrame Where

Knowledge Sources	Daft Daft Docs
Domains	Data_Engineering, Data_Transformation
Last Updated	2026-02-08 00:00 GMT

Overview

Concrete tool for filtering DataFrame rows based on a boolean predicate expression provided by the Daft library.

Description

The where method on Daft's DataFrame class filters rows by evaluating a predicate expression and retaining only rows where the predicate is True. It accepts either a Daft Expression object or a SQL expression string (parsed via sql_expr). Rows where the predicate evaluates to False or Null are discarded. The filter method is an alias that delegates to where.

Usage

Use df.where() or equivalently df.filter() when you need to subset a DataFrame based on conditions. This is a method on DataFrame instances and requires no additional imports beyond Daft itself.

Code Reference

Source Location

• Repository: Daft
• File: daft/dataframe/dataframe.py
• Lines: L2357-2405

Signature

def where(self, predicate: Expression | str) -> DataFrame

Import

import daft

# Method on DataFrame - no separate import needed
df.where(daft.col("x") > 5)
df.where("x > 5")  # SQL expression string

I/O Contract

Inputs

Name	Type	Required	Description
predicate	Expression or str	Yes	Boolean predicate expression. Can be a Daft Expression or a SQL expression string.

Outputs

Name	Type	Description
return	DataFrame	A new DataFrame containing only rows where the predicate evaluated to True

Usage Examples

Basic Usage

import daft

df = daft.from_pydict({"x": [1, 2, 3], "y": [4, 6, 6], "z": [7, 8, 9]})

# Filter with Expression predicate
result = df.where((df["x"] > 1) & (df["y"] > 1))
result.collect()
# Output:
# x: [2, 3]
# y: [6, 6]
# z: [8, 9]

SQL Expression String

import daft

df = daft.from_pydict({"x": [1, 2, 3], "y": [4, 5, 6], "z": [7, 9, 9]})

# Filter using a SQL expression string
result = df.where("z = 9 AND y > 5")
result.collect()
# Output:
# x: [3]
# y: [6]
# z: [9]

Related Pages

Implements Principle

• Principle:Eventual_Inc_Daft_Row_Filtering

Requires Environment

• Environment:Eventual_Inc_Daft_Python_PyArrow_Core