rapidsai/cudf

[FEA] efficient way to truncate by month

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#18,650 opened on May 3, 2025

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Pythonfeature requestgood first issuelibcudf

Description

Is there an efficient way to truncate a Series by month / quarter in cuDF?

https://docs.rapids.ai/api/cudf/latest/user_guide/api_docs/api/cudf.core.series.datetimeproperties.floor/ dt.floor doesn't support month / year / quarter

In pandas I can either, depending on the dtype backend:

  • drop to numpy and use astype('datetime64["3M"]'))
  • drop to PyArrow and use pc.floor_temporal

Any suggestion for cuDF?

Example: given

import cudf
from datetime import datetime

s = cudf.Series([datetime(2020, 2, 4)])
s.dt.truncate('3 months')  # Not valid syntax, I know :)

I'd like to end up with

'2020-01-01'

Contributor guide

Tech stack
pythoncpp
Domain
dataperformance
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Basic PythonBasic cuDF
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Investigate the current implementation of truncation in cuDF's datetime functionality. Look at the `dt.floor` method and how it currently supports only certain frequencies. The issue suggests a need for month/quarter truncation. Review the relevant C++ source files in `cpp/src/datetime/` and Python wrappers in `python/cudf/cudf/core/series/datetime.py`. Consider if a new kernel is needed or if existing kernels can be extended. Also check if any assignee has started work or if there are discussions in the comments that clarify the approach. The user mentions pandas and PyArrow alternatives, so compare those implementations.
[FEA] efficient way to truncate by month · rapidsai/cudf#18650 | Good First Issue