tidy3

dplyr-style lazy data manipulation for Python, powered by Polars.

• Readable multi-line pipes (>> ≈ R’s |>)
• Works locally (VS Code, terminal, JupyterLab) or under CRAFT / gpudev
• Lazy until collect() / plot / preview (LIMIT n only)
• Handoffs for ML (to_numpy, pandas/Arrow) and optional plot3

CRAFT/%gpu is an optional remote path. The default product surface is a normal Python environment on your machine.

Install

pip install "tidy3[jupyter]"

Optional extras:

Extra	Adds
jupyter	IPython extension for multi-line >> pipes
plot3	plot3 for >> ggplot(...)
excel	write_excel

The latest unreleased code installs straight from GitHub:

pip install "tidy3[jupyter] @ git+https://github.com/rleyvasal/tidy3"

To work on tidy3 itself:

git clone https://github.com/rleyvasal/tidy3 && cd tidy3
python3 -m venv .venv
source .venv/bin/activate          # Windows: .venv\Scripts\activate
pip install -e ".[dev,jupyter]"
python -m pytest -q

Quick start

The examples need no downloads: each section builds the small tables it uses. cars is four columns of R's mtcars:

from tidy3 import tidy, scan_parquet, filter, mutate, group_by, summarise, col, n, mean

cars = tidy({
    "mpg": [21.0, 21.0, 22.8, 21.4, 18.7, 18.1, 14.3, 24.4, 22.8, 19.2, 17.8,
            16.4, 17.3, 15.2, 10.4, 10.4, 14.7, 32.4, 30.4, 33.9, 21.5, 15.5,
            15.2, 13.3, 19.2, 27.3, 26.0, 30.4, 15.8, 19.7, 15.0, 21.4],
    "cyl": [6, 6, 4, 6, 8, 6, 8, 4, 4, 6, 6, 8, 8, 8, 8, 8, 8, 4, 4, 4, 4, 8,
            8, 8, 8, 4, 4, 4, 8, 6, 8, 4],
    "hp": [110, 110, 93, 110, 175, 105, 245, 62, 95, 123, 123, 180, 180, 180,
           205, 215, 230, 66, 52, 65, 97, 150, 150, 245, 175, 66, 91, 113, 264,
           175, 335, 109],
    "wt": [2.62, 2.875, 2.32, 3.215, 3.44, 3.46, 3.57, 3.19, 3.15, 3.44, 3.44,
           4.07, 3.73, 3.78, 5.25, 5.424, 5.345, 2.2, 1.615, 1.835, 2.465, 3.52,
           3.435, 3.84, 3.845, 1.935, 2.14, 1.513, 3.17, 2.77, 3.57, 2.78],
})
cars.write_parquet("cars.parquet")      # a file to scan lazily below

result = (
    scan_parquet("cars.parquet")        # lazy: reads only when needed
    >> filter(col("mpg") > 20)
    >> mutate(km=col("mpg") * 1.609)
    >> group_by("cyl")
    >> summarise(n=n(), avg=mean("mpg"))
)

result                              # TidyFrame preview; keep piping if needed
polars_df = result.collect()        # materialize as Polars
pandas_df = result.collect(as_="pandas")
numpy_array = result.collect(as_="numpy")

For in-memory data, start from tidy(cars) instead of the scan. Starting from scan_parquet(), scan_csv(), or scan_ipc() avoids first building a pandas copy and lets Polars push projections and filters into the file scan.

With the Jupyter extension loaded you can omit the outer parentheses — the kernel rewrites multi-line >> pipes before parse.

Save results

Write a pipeline directly without first calling collect():

result.write_parquet("summary.parquet")  # recommended for data pipelines
result.write_csv("summary.csv")
result.write_ipc("summary.arrow")        # Arrow IPC / Feather

With the default Polars backend, these execute the lazy plan and stream its result to disk, avoiding a second fully materialized DataFrame in memory. The same methods also work with backend="pandas". GPU writers execute the plan on the GPU, then materialize before serialization because current GPU file sinks are not stable across all formats; auto and streaming retain direct lazy sinks.

Choose how Polars executes when the plan is materialized or written:

result.collect(engine="auto")             # default: let Polars choose
result.collect(engine="streaming")        # execute in streaming batches

result.write_parquet("summary.parquet", engine="streaming")
result.write_ipc("summary.arrow", engine="auto")

On an NVIDIA GPU with pip install cudf-polars, Polars runs what it can on the GPU and falls back to the CPU for the rest:

result.collect(engine="gpu")
result.write_csv("summary.csv", engine="gpu")

The same engine= argument is available on to_polars(), to_pandas(), to_arrow(), and write_excel(). It applies only to the default Polars backend. For a GPU run that must not silently fall back to CPU, pass engine=polars.GPUEngine(raise_on_fail=True); the benchmark suite does this automatically whenever --polars-engine gpu is selected.

Excel output is intended for smaller reporting datasets and must materialize the result:

pip install "tidy3[excel]"

result.write_excel(
    "summary.xlsx",
    worksheet="Summary",
    autofit=True,
    freeze_panes="A2",
)

You can still collect first when another library needs the result:

result.collect().write_csv("summary.csv")          # Polars API
result.collect(as_="pandas").to_csv("summary.csv", index=False)

VS Code (local IDE)

tidy3 is a normal package. No CRAFT, SolveIt, or remote kernel is required.

One-time setup

1. Open your project folder in VS Code.
2. Create a virtual environment and install tidy3 (terminal in VS Code):

python3 -m venv .venv
source .venv/bin/activate
pip install "tidy3[jupyter]"

3. Select it: Command Palette → Python: Select Interpreter → ./.venv/bin/python.
4. Recommended extensions: Python (includes Pylance) and Jupyter. Optional: Polars is a library dependency, not a VS Code extension.

Type checker / red squiggles under >> pipes

You do not need a special tidy3 VS Code extension. Pylance is enough once tidy3 is installed (types ship with py.typed).

1. Interpreter = your project's .venv (Command Palette → Python: Select Interpreter).
2. Import the names you use in that cell/file:

from tidy3 import tidy, select, filter, arrange, slice_max, col, desc

3. Reload the window if squiggles linger: Developer: Reload Window.

If a name is still underlined, it is usually “not imported in this cell”, not a pipe typing bug. Runtime green + import present ⇒ safe to ignore residual noise.

Scripts (.py)

Parentheses around multi-line >> pipes are required (standard Python):

# analysis.py
from tidy3 import tidy, filter, mutate, group_by, summarise, col, n, mean

result = (
    tidy({"cyl": [4, 4, 6], "mpg": [22.0, 24.0, 18.0]})
    >> filter(col("mpg") > 20)
    >> mutate(km=col("mpg") * 1.609)
    >> group_by("cyl")
    >> summarise(n=n(), avg=mean("mpg"))
)

print(result.collect())                 # Polars DataFrame
print(result.collect(as_="pandas"))     # for sklearn / export
# features = result.to_numpy(columns=["avg"], dtype="float32")

Run:

python analysis.py
# or VS Code: Run Python File

Interactive window / notebook

1. Create analysis.ipynb (or open the Interactive Window).
2. Pick the same .venv kernel (Select Kernel → your tidy3 venv).
3. In the first cell, either import normally or load the pipe rewriter:

# Option A — plain Python (parentheses required)
from tidy3 import tidy, filter, col

# Option B — multi-line >> without outer parentheses
%load_ext tidy3.jupyter

With the extension loaded:

tidy(cars)
>> filter(col("mpg") > 20)
>> mutate(km=col("mpg") * 1.609)

A cell can mix pipes with comments and other code. Each line that starts with >> continues the statement above it, even across comment and blank lines; a + line continues a pipe into plot3 layers:

from plot3 import aes, geom_point, ggplot

# Cars with good mileage
good = tidy(cars)
>> filter(col("mpg") > 20)   # fast enough
# keep what we plot
>> select("mpg", "hp")

good
>> ggplot(aes(x="hp", y="mpg"))
+ geom_point()

Inside an indented block (if, for, def), wrap the pipe in parentheses.

Partial pipes for debugging:

%%tidy3_run
tidy(cars)
>> filter(col("mpg") > 20)

%tidy3_pipes on|off|status

Handoffs from a local session

# Algorithms / sklearn
df = result.collect(as_="pandas", columns=["cyl", "avg"], arrow_backed=True)

# NumPy → PyTorch (CPU)
import numpy as np
# import torch
X = result.to_numpy(columns=["avg"], dtype=np.float32, writable=True, order="c")
# t = torch.from_numpy(X)

# plot3 (optional; install plot3 separately)
# from plot3 import aes, geom_point, ggplot
# result >> ggplot(aes(x="cyl", y="avg")) + geom_point()

Local vs CRAFT at a glance

	Local (VS Code)	CRAFT / %gpu
Install	pip install tidy3 in a venv	Addon seed to remote kernel
Paths	Your machine	Paths on the GPU host
Pipes	Parentheses in .py; extension optional in notebooks	Same extension after seed
Data size	Laptop RAM / local Polars	Remote GPU box + large files
Default for new users	Yes	Optional power path

plot3 (optional)

plot3 is a separate package. Install it with tidy3's plot3 extra:

pip install "tidy3[plot3]"

import numpy as np
from plot3 import aes, geom_point, ggplot

# A made-up 3D scan: 5,000 points on a hill, with an intensity per point
rng = np.random.default_rng(0)
xy = rng.uniform(-3, 3, (2, 5_000))
big = {
    "x": xy[0],
    "y": xy[1],
    "z": np.exp(-(xy**2).sum(axis=0) / 4),
    "intensity": rng.uniform(0, 30, 5_000),
}

tidy(big)
>> filter(col("intensity") > 10)
>> select("x", "y", "z", "intensity")
>> ggplot(aes(x="x", y="y", z="z", colour="intensity"))
+ geom_point()

The method handoff remains available as tidy(df).ggplot(aes(...)). The bridge materializes to pandas for plot3; aggregate large data first.

CRAFT / gpudev / SolveIt

Use this when you work in SolveIt (dialog notebook) and/or data lives on a GPU host via CRAFT %gpu. Local VS Code setup above is enough for everyday laptop work.

SolveIt load (tidy3 + plot3)

%local
%run /path/to/gpudev/CRAFT.py                 # if you need %gpu
%run /path/to/gpudev/addons/tidy3.py
%run /path/to/gpudev/addons/plot3.py          # ggplot / %plot3

One command — works local and under %gpu (CRAFT is auto-detected):

%run /app/data/gpudevd/tidy3/tidy3.py
# or
%run /path/to/tidy3/tidy3.py
%run /path/to/tidy3/load.py          # same loader

That puts src/ on the path, injects the API, and turns on multi-line >> plus R-style bare names / backticks / ~ (optional ! sugar only inside tidy3 verb calls — shell cells like !pip install are never rewritten). If CRAFT is already loaded (or becomes connected on %gpu), the same cell also registers remote seeding — no second command.

%local
%run /app/data/gpudevd/tidy3/tidy3.py
%run /app/data/gpudevd/plot3/plot3.py
# only when you need the GPU:
%run /path/to/gpudev/CRAFT.py
%gpu

After a normal editable install you can also use:

%load_ext tidy3.jupyter
%load_ext plot3

With %gpu (remote compute)

%local
%run …/CRAFT.py
%run …/addons/tidy3.py
%run …/addons/plot3.py
%gpu

Under %gpu, cells run on the remote kernel (separate namespace + filesystem). Both addons push their source to the remote over the CRAFT channel (tidy3.craft / plot3.craft), install polars/pandas if missing, and load Jupyter extensions there. Re-seed after kernel surgery with seed_tidy3_remote(force=True) / seed_plot3_remote(force=True).

# after %gpu — paths are on the GPU box
scan_parquet("/home/gpudev/data/huge.parquet")
>> filter(col("year") >= 2020)
>> group_by("region")
>> summarise(n=n(), avg=mean("value"))
>> ggplot(aes(x="region", y="avg")) + geom_col()

%plot3 is registered as a host-local magic (viewer + SolveIt red-eye stay on the dialog machine) even while Python cells run remote.

Partial run (any Jupyter / SolveIt)

• Run Selected Text (if the UI has it): highlight a pipe prefix → run
• Own cell with only the prefix
• %%tidy3_run with the prefix pasted in

%%tidy3_run
tidy(cars)
>> filter(col("mpg") > 20)

%tidy3_pipes on|off|status
%tidy3_mask on|off|status    # R-style bare names / backticks

EDA inspection

names(cars)       # list[str]
colnames(cars)    # paste-ready selectors for select(...)
cars.columns      # same list as names
summary(cars)     # count, null_count, n_unique, mean, std, min, 25%, 50%, 75%, max
describe(cars)    # alias of summary (pandas-style name)

R-style bare names & backticks

With the extension loaded (CRAFT addon or %load_ext tidy3.jupyter), cells may omit many col("…") / quotes:

cars >> filter(mpg > 20) >> mutate(z = if_else(cyl > 4, 1, 0))
cars_space = cars >> rename(`hp new` = hp)             # a name with a space
cars_space >> mutate(ratio = `hp new` / cyl) >> select(`hp new`, ratio)
cars >> select(~starts_with("w"))      # prefer ~ for negation
cars >> select(!starts_with("w"))      # optional Jupyter sugar → ~ (tidy3 only)
ggplot(cars, aes(x=wt, y=mpg)) + geom_point()          # with plot3
ggplot(cars_space, aes(x=`hp new`, y=mpg)) + geom_point()

!pip install … and other notebook shell commands are not rewritten.

• Expression context (filter, mutate RHS, …): bare name → col("name")
• Selector context (select, group_by, …): bare name → "name"
• Backticks: `any column name` for spaces / odd identifiers
• Columns named like Python builtins or tidy3 helpers (id, type, max, n) work bare wherever only a column makes sense: filter(id > 1), select(id, type), arrange(desc(id)), mutate(z = max * 2). Passed as a function, as in across(everything(), mean), they stay functions.
• Columns win over notebook variables, as in dplyr: with x = 100 in the notebook, filter(x > limit) still compares the column x, and limit is your variable because there is no column called limit. Use env.x for the variable when a column has the same name (dplyr's .env$x), or col("x") to insist on the column. Within one mutate(), a column made earlier counts: mutate(y = x * 2, z = y + 1). Calls skip non-functions like R does, so n() still counts rows after n = 7.
• plot3 aes / facet_wrap use the same style in Jupyter

Export notebook → plain Python script (nb_export)

R-style is the authoring form. For automation / CI, export rewrites it to stock CPython (nbdev-style build artifact):

from tidy3 import nb_export

nb_export("analysis.ipynb", "analysis_pipeline.py")
# only cells marked #| export (nbdev-style):
nb_export("analysis.ipynb", "lib.py", only_export=True)

python -m tidy3 export analysis.ipynb -o analysis_pipeline.py
python -m tidy3 export analysis.ipynb -o lib.py --only-export

Cell directives:

Directive	Meaning
#| export	include when --only-export / only_export=True
#| skip	never export (debug / interactive cells)

What export does:

1. Collects code cells (skips markdown)
2. Applies the same bare-name / backtick / multi-line >> transforms as Jupyter
3. Applies plot3 aes masking when plot3 is installed
4. Turns internal sentinels into public API (col("mpg"), not __tidy3_col__)
5. Comments pure notebook magics (%run, …); best-effort rewrite of %plot3

The notebook stays the source of truth; re-export instead of hand-editing the .py. Explicit col("x") / aes(x="x") still work everywhere as a compatible subset.

Optional: run an unexported R-style script with the same transforms:

python -m tidy3 run job.py

Symlink addons (CRAFT layout)

cd /path/to/gpudev/addons
ln -sfn /path/to/tidy3 tidy3
ln -sfn /path/to/plot3 plot3

API

Area	Symbols
Export	nb_export, transform_source, python -m tidy3 export / run
Frame	tidy, scan_parquet, scan_csv, scan_ipc, TidyFrame
Output	collect, to_numpy, TidyFrame.write_parquet, TidyFrame.write_csv, TidyFrame.write_ipc, TidyFrame.write_excel
Rows	filter, filter_out, arrange, distinct, slice, slice_head, slice_tail, slice_min, slice_max, slice_sample, head, sample_n, sample_frac
Columns	mutate, transmute, select, drop, rename, rename_with, relocate, pull, glimpse
Groups	group_by, rowwise, ungroup, with_groups, group_split, group_map, group_modify, group_walk, group_nest, nest_by, group_data, group_keys, group_rows, group_size, group_indices, group_vars, groups, n_groups, group_trim, summarise, reframe, count, tally, add_count, add_tally
Missing data	drop_na, replace_na, fill, complete, expand, nesting, crossing, expand_grid, full_seq, uncount
Reshape	pivot_longer, pivot_wider, separate, separate_longer_delim, separate_wider_delim, separate_wider_regex, separate_wider_position, separate_longer_position, unite, nest, unnest, unnest_longer, unnest_wider, unnest_auto, chop, unchop, hoist, pack, unpack
Joins	left_join, right_join, inner_join, full_join, semi_join, anti_join, cross_join, nest_join
Join specs	join_by, eq, ge, gt, le, lt, closest, between, within, overlaps
Bind/set	bind_rows, bind_cols, union, union_all, intersect, setdiff, symdiff, setequal
Row mutation	rows_insert, rows_append, rows_update, rows_patch, rows_upsert, rows_delete
Selectors	everything, col_range/cols_between, last_col, group_cols, starts_with, ends_with, contains, matches, num_range, all_of, any_of, where; set ops | & - ~/!/-helper; predicates is_numeric, is_integer, is_float, is_string/is_character, is_bool/is_boolean, is_datetime, is_categorical, is_temporal
Column-wise	across, if_any, if_all, pick, c_across
Materialize	collect, pull, glimpse, peek
Expr	col, n, mean, sum, min, max, median, std/sd, var, any, all, first, last, nth, near, na_if, between, consecutive_id, case_match, recode, ranking/window helpers, n_distinct, coalesce, if_else, case_when, recode_values, replace_values, replace_when, when_any, when_all, order_by, with_order
Jupyter	%load_ext tidy3.jupyter, %tidy3_run, %%tidy3_run, %tidy3_pipes
Partial	partial_run, maybe_rewrite_cell, normalize_pipe_source
Escape	TidyFrame.with_polars(fn)

API maturity

tidy3 is alpha. Symbols work today, but not every verb is equally polished for production pipelines or R byte-for-byte parity. Prefer the stable core when you need predictable performance and semantics.

Tier	Intent	Symbols / areas
Stable core	Daily driver: declarative dplyr on Polars, dual-backend tests, R oracle where installed	tidy, scan_*, filter, filter_out, mutate, transmute, select, drop, rename, relocate, arrange, distinct, group_by, ungroup, summarise/summarize, count, tally, add_count, add_tally, equality joins (left/right/inner/full/semi/anti/cross), bind_rows/bind_cols, set ops (union, union_all, intersect, setdiff, symdiff, setequal), head/slice/slice_head/slice_tail/slice_min/slice_max, core expr helpers (col, n, mean, sum, …), tidyselect basics, collect and file writers
Growing	Feature-complete enough for real work; more edge cases and schema-discovery cost	tidyr missing/reshape (drop_na, replace_na, fill, complete, expand, pivot_*, separate, unite, nest/unnest*), across/if_any/if_all/pick/c_across, rowwise, reframe, rename_with, join_by inequality joins, nest_join, rows_*, advanced ranking/window helpers, NumPy/to_numpy handoff
Experimental	Correctness-first or Python-callback paths; may materialize eagerly or lag R oracle coverage	group_split, group_map, group_modify, group_nest, with_groups, hoist, pack, unpack, separate_longer_delim, separate_wider_delim, stochastic sampling (sample_n, sample_frac, slice_sample)

Performance note: the stable core is the path that tracks raw Polars and beats pandas on realistic sizes. group_nest compiles to a Polars group_by().agg(struct) plan and is typically faster than building nested pandas DataFrames by hand; for counts alone use count()/tally() instead of nesting. Python-callback verbs (group_map / group_modify / group_split) still materialize and loop in Python — fine for small groups, not for hot large-data paths. Prefer declarative summarise when performance matters.

Backends

The default engine is Polars lazy. For 1:1 engine comparisons (e.g. against datar, which is pandas-only) the same pipeline also runs on an eager pandas backend:

import pandas as pd

df = pd.DataFrame({"x": [-1.5, 0.5, 2.0], "y": [10, 20, 30]})

tidy(df, backend="pandas") >> filter(col("x") > 0)   # per frame
options(backend="pandas")                            # session default
options(backend="polars")                            # back to the default

Expressions (col("x") * 2, mean("y"), comparisons, cum_sum, …) are backend-neutral: they compile to pl.Expr on polars and evaluate natively on pandas, with dplyr window semantics after group_by on both. The pandas backend covers the documented verb/expression subset; anything polars-specific raises a clear error pointing back to backend="polars".

Tidy-select and column-wise operations

Selectors work anywhere columns are selected by select, drop, relocate, or rename_with. Combine them with | (union), & (intersection), - (difference), or ~ (complement / negation):

df = tidy({
    "id": [1, 2, 3],
    "label": ["a", "b", "c"],
    "measure_1": [0.5, 0.7, 0.2],
    "measure_2": [1.5, 1.1, 0.9],
    "mpg": [21.0, 22.8, 18.7],
    "cyl": [6, 4, 8],
    "hp": [110, 93, 175],
    "tmp_flag": [True, False, True],
    "hp_raw": ["110", "93", "175"],
})

df >> select("id", starts_with("measure_"), last_col())
df >> select(~starts_with("tmp_"))             # preferred: Python-native invert
df >> select(where(is_numeric) & ~starts_with("id"))
df >> select(cols_between("mpg", "hp"))        # inclusive column range
df >> select(everything() - ends_with("_raw"))
df >> relocate(where(is_numeric), after="label")

Negation: prefer ~. It is always valid Python (Expr / Selector implement __invert__) and works in scripts, notebooks, and exports with no preparser.

In Jupyter/SolveIt only, ! is optional R-like sugar inside tidy3 verb calls (e.g. select(!starts_with("tmp_")) → ~). Outside tidy3 contexts ! is left alone so shell cells stay literal (!pip install …).

where receives column dtypes; portable predicates include is_numeric, is_string, is_boolean, and is_temporal. all_of(names) is strict about missing columns while any_of(names) silently ignores them.

Reshape and missing data

The familiar tidyr operations work as pipe verbs or TidyFrame methods on both backends:

from tidy3 import (
    complete, drop_na, fill, nest, pivot_longer, pivot_wider, replace_na,
    separate, starts_with, tidy, unite, unnest, unnest_longer,
)

# Weekly readings per visit; the patient id is only on each patient's first row
measurements = {
    "patient_id": ["p1", None, "p2", None],
    "visit": ["baseline", "follow-up", "baseline", "follow-up"],
    "week_1": [5.1, 4.8, 6.0, None],
    "week_2": [5.3, None, 6.2, 6.4],
}
long_measures = {
    "store": ["A", "A", "B", "B"],
    "quarter": ["Q1", "Q2", "Q1", "Q2"],
    "sales": [100, 120, 90, 95],
    "cost": [60, 70, 55, 50],
}
visits = {"subject": [1, 2], "mean_1": [5.0, 6.1], "mean_2": [5.4, 6.3],
          "sd_1": [0.4, 0.5], "sd_2": [0.3, 0.6]}
labels = {"code": ["north-1", "north-2", "south-1"]}
events = {
    "team": ["red", "red", "blue", "blue"],
    "time": [1, 2, 1, 2],
    "value": [3.5, 4.0, 2.5, 3.0],
    "score": [95, None, 88, 91],
    "items": [["a", "b"], ["c"], [], ["d", "e"]],
}
values = {"score": [7, None, 9], "required_field": ["x", "y", None]}
observations = {"subject": ["s1", "s1", "s2"], "visit": [1, 2, 1], "score": [3, None, 4]}

long = (
    tidy(measurements)
    >> fill("patient_id", direction="down")
    >> pivot_longer(
        starts_with("week_"),
        names_to="week",
        names_prefix="week_",
        values_to="reading",
        values_drop_na=True,
    )
)

wide = long >> pivot_wider(
    names_from="week",
    values_from="reading",
    names_prefix="week_",
    values_fill=0,
)

# Multiple measures use tidyr's value-first names (sales_Q1, cost_Q1).
wide_measures = tidy(long_measures) >> pivot_wider(
    names_from="quarter", values_from=["sales", "cost"]
)

# .value takes output value-column names from the input column names.
tidy(visits) >> pivot_longer(
    starts_with(("mean_", "sd_")),
    names_to=[".value", "visit"],
    names_sep="_",
)

parts = tidy(labels) >> separate("code", ["region", "id"], sep="-")
parts >> unite("code", "region", "id", sep="-")
tidy(events) >> unnest_longer("items", indices_to="item_index")
tidy(values) >> replace_na({"score": 0}) >> drop_na("required_field")

tidy(observations) >> complete(
    "subject", "visit", fill={"score": 0}, explicit=False
)

nested = tidy(events) >> nest("records", cols=["time", "value"])
restored = nested >> unnest("records")

Build grids and repeat rows like tidyr:

expand_grid(store=["A", "B"], week=[1, 2, 3])          # every combination, as given
crossing(store=["B", "A", "B"], week=[2, 1])           # distinct values, sorted
tidy({"item": ["pen", "cup"], "n": [2, 1]}) >> uncount("n", id="copy")

# Fill in missing years: full_seq() spans min to max in steps of 5
tidy({"country": ["A", "A", "B"], "year": [1952, 1962, 1957], "pop": [1.0, 2.0, 3.0]}) >> complete(
    "country", year=full_seq("year", 5)
)

Split text by pattern or position, and move between lists and rows:

codes = tidy({"id": [1, 2], "code": ["ab-12", "cd-3"], "date": ["20240115", "20231201"]})
codes >> separate_wider_regex("code", [("letters", "[a-z]+"), "-", ("number", "[0-9]+")])
codes >> separate_wider_position("date", [("year", 4), ("month", 2), ("day", 2)])
codes >> separate_longer_position("code", 2)            # "ab", "-1", "2", ...

chopped = tidy({"g": ["a", "a", "b"], "x": [1, 2, 3]}) >> chop("x")
chopped >> unchop("x")                                   # back to one row per value

In separate_wider_regex(), a bare string is matched but not kept; in separate_wider_position(), a bare number is a width that is skipped. unnest_auto() picks unnest_wider() for named elements and unnest_longer() otherwise.

expand() and complete() take named values like this too. The values keep the column's type, so a whole-number year stays whole (R's full_seq() would make it a decimal).

fill(..., by=...) provides temporary grouping, while an existing group_by() is respected automatically. Most Polars operations add only lazy plan nodes. pivot_wider() must know its output schema, so it discovers the distinct names_from values unless names=[...] is supplied; providing names avoids that metadata query for known categories. unnest_wider() similarly discovers the width of unnamed list values.

pivot_wider() accepts multiple names_from and values_from columns. As in tidyr, values that the id and name columns do not uniquely identify become list columns with a warning; pass values_fn="list" to ask for lists, or values_fn="mean" (sum, first, …) to summarise duplicates. pivot_longer() supports the .value sentinel, and separate(convert=True) performs R-style logical/numeric inference on both backends. Schema-dependent reshape and conversion operations issue a metadata-only query on Polars.

Use across as a positional argument to mutate, transmute, or summarise. Python name templates accept {col} and {fn}; dplyr-style {.col} and {.fn} are accepted too. Use cur_column() inside a function when its calculation depends on the selected column name, and cur_group()["group_name"] when it depends on a grouped key:

df = tidy({
    "id": [1, 2, 3, 4],
    "team": ["red", "red", "blue", "blue"],
    "region": ["north", "north", "south", "south"],
    "year": [1999, 2004, 2011, 2016],
    "target": [2.0, 2.0, 1.0, 1.0],
    "x": [1.234, 2.5, -0.75, 3.0],
    "x_adj": [1.1, 2.4, -0.7, 2.9],
    "math_score": [80, -5, 92, 70],
    "art_score": [-1, -3, 88, 75],
})

tidy(df)
>> mutate(across(starts_with("x"), lambda x: x.round(2)))
>> filter(if_any(ends_with("_score"), lambda x: x > 0))
>> group_by("team")
>> summarise(
    across(
        where(is_numeric),
        {"mean": mean, "sd": std},
        names="{col}_{fn}",
    )
)

tidy(df) >> mutate(
    across(starts_with("x"), lambda x: x + len(cur_column()))
)

tidy(df) >> group_by("team", "target") >> mutate(
    across(starts_with("x"), lambda x: x - cur_group()["target"])
)

tidy(df) >> group_by("team") >> mutate(
    across(starts_with("x"), lambda x: x + cur_group_id())
)

Functions passed to across can return a mapping of named expressions. Pass unpack=True to expand those fields into regular columns; use an {outer}/{inner} template to control the resulting names:

tidy(df) >> mutate(
    across(
        starts_with("x"),
        lambda x: {"double": x * 2, "plus_one": x + 1},
        unpack="{outer}__{inner}",
    )
)

Row-wise operations and reframing

rowwise evaluates ordinary window/aggregate expressions one row at a time. Its optional tidy-select arguments are identifier columns preserved by summarise. Use c_across for row-wise reductions; grouping identifiers are automatically excluded:

tidy(df)
>> rowwise("id")
>> mutate(
    total=sum(c_across(ends_with("_score"))),
    average=mean(c_across(ends_with("_score"))),
)
>> ungroup()

pick represents a selected set as one structured column and supports common horizontal reductions without requiring rowwise:

tidy(df) >> mutate(total=pick(ends_with("_score")).sum())
tidy(df) >> mutate(scores=pick(ends_with("_score")))

reframe accepts vector-valued expressions, recycles scalar results within each group, and always returns an ungrouped frame:

tidy(df)
>> group_by("team")
>> reframe(score=col("math_score"), team_mean=mean("math_score"))

dplyr-compatible evaluation controls

Assignments in one mutate() are evaluated from left to right, so later expressions can use columns created earlier. Independent assignments are still fused into one backend operation:

tidy(df) >> mutate(
    doubled=col("x") * 2,
    squared=col("doubled") ** 2,
    keep="used",                  # all, used, unused, or none
    before="x",
)

distinct("id") returns only the grouping columns and id, matching dplyr. Use distinct("id", keep_all=True) to retain the first complete row. Multi-level summaries default to dropping only the final group; override this with groups="drop", "drop_last", "keep", or "rowwise".

Computed and additive groups and partial ungrouping are supported:

tidy(df)
>> group_by("region")
>> group_by(add=True, decade=col("year") // 10)
>> ungroup("decade")

Ask about the groups with dplyr's group functions, called or piped:

by_team = tidy(df) >> group_by("team")

group_keys(by_team)        # one row per group, sorted by key
group_size(by_team)        # [2, 2]
group_rows(by_team)        # [[3, 4], [1, 2]]: 1-based row positions
by_team >> group_indices() # each row's 1-based group number
by_team >> group_walk(lambda part, key: print(key["team"], part.collect().height))

tidy(df) >> nest_by("team")  # one row per team, other columns nested in `data`

Groups come in dplyr's order, sorted by key with missing last, in these functions and in group_split(), group_map(), group_modify(), and group_nest(). Row positions are 1-based, as in dplyr and slice(); subtract 1 to index a pandas frame or NumPy array.

Aggregates accept na_rm= and default to False, matching dplyr: a missing value propagates unless removal is requested explicitly. Use mean("x", na_rm=True) to ignore missing values.

Row mutation and advanced joins

The SQL-inspired row verbs use y's first column as the key by default, or accept explicit by= keys. y may contain any subset of x's columns:

accounts = {"id": [1, 2, 3], "owner": ["Ana", "Ben", None], "balance": [100.0, None, 50.0]}
new_accounts = {"id": [3, 4], "owner": ["Cy", "Dee"], "balance": [0.0, 75.0]}
corrections = {"id": [2, 3], "owner": ["Bob", "Cy"], "balance": [20.0, 999.0]}
latest = {"id": [1, 5], "owner": ["Ana", "Eve"], "balance": [120.0, 10.0]}
retired = {"id": [4]}

tidy(accounts)
>> rows_insert(new_accounts, by="id", conflict="ignore")
>> rows_patch(corrections, by="id")       # only replaces missing values
>> rows_upsert(latest, by="id")           # update matches, append new keys
>> rows_delete(retired, by="id")

rows_insert supports conflict="error"|"ignore"; update, patch, and delete support unmatched="error"|"ignore". Polars validates these policies lazily when the plan is collected.

join_by accepts same-name equality keys, (left, right) equality pairs, or (left, operator, right) conditions. Named helpers are clearer for advanced joins:

from datetime import date

sales = tidy({
    "id": [1, 1, 2, 2, 3],
    "region": ["north", "north", "south", "south", "south"],
    "year": [2024, 2025, 2024, 2025, 2025],
    "sale_date": [date(2025, 1, 10), date(2025, 3, 2), date(2025, 1, 5),
                  date(2025, 2, 20), date(2025, 2, 1)],
    "amount": [120.0, 80.0, 45.0, 60.0, 30.0],
})
promos = tidy({
    "id": [1, 1, 2],
    "promo_date": [date(2025, 1, 1), date(2025, 2, 1), date(2025, 2, 15)],
    "discount": [0.10, 0.15, 0.05],
})
points = tidy({"point": [1, 5, 12]})
ranges = tidy({"lower": [0, 10], "upper": [6, 20], "band": ["low", "high"]})
segments = tidy({"lo": [0, 8], "hi": [4, 12]})
regions = tidy({"start": [3, 10], "end": [9, 15], "name": ["A", "B"]})

sales
>> left_join(
    promos,
    by=join_by("id", ge("sale_date", "promo_date")),
)

# One nearest earlier promotion per sale
sales
>> left_join(
    promos,
    by=join_by("id", closest(ge("sale_date", "promo_date"))),
)

points >> inner_join(ranges, by=join_by(between("point", "lower", "upper")))
segments >> inner_join(regions, by=join_by(overlaps("lo", "hi", "start", "end")))

Advanced specifications work with left/right/inner/full/semi/anti joins. Polars uses its native inequality-join plan when no equality partition is needed; equality-partitioned inequalities first reduce candidates by key.

Per-operation grouping and portable helpers

Use by= when grouping is needed for one operation only. It accepts the same tidy-select specifications as select() and returns an ungrouped result:

tidy(sales)
>> mutate(region_average=mean("amount"), by="region")
>> filter(col("amount") > mean("amount"), by="region")

tidy(sales) >> summarise(total=sum("amount"), by=["region", "year"])
tidy(sales) >> slice_max("amount", n=2, by="region")

by= is supported by mutate, transmute, filter, filter_out, summarise, reframe, slice, and every slice_* variant. Like dplyr, it cannot be combined with an already grouped or rowwise frame.

Portable helpers run with the same grouped semantics on both backends:

tidy(events) >> mutate(
    row=row_number(),
    rank=dense_rank("score"),
    previous=lag("score"),
    running_average=cummean("score"),
    label=case_when(
        (col("score").is_null(), "missing"),
        (col("score") >= 90, "high"),
        default="other",
    ),
    by="team",
)

dplyr 1.2's recoding helpers map values with (values, replacement) pairs, where None matches missing values, or with a from_=/to= lookup table:

tidy(events) >> mutate(
    team_name=recode_values("team", ("red", "Red Rockets"), ("blue", "Blue Jays")),
    score=replace_values("score", (None, 0)),
    capped=replace_when("value", (col("value") > 3.5, 3.5)),
    flagged=when_any(col("score") >= 90, col("value") < 3),
)

recode_values() builds a new column (unmatched values become default, or an error with unmatched="error"); replace_values() and replace_when() change some values and keep the rest. when_any() and when_all() combine conditions with | and &; na_rm=True ignores missing values. They supersede case_match() and recode(), which still work.

Ranking helpers are row_number, min_rank, dense_rank, percent_rank, cume_dist, and ntile. Window and value helpers include lead, lag, cummean, cumall, cumany, n_distinct, coalesce, if_else, and case_when. lead, lag, first, last, and nth accept order_by=. For any other window expression, order_by() computes it as if the rows were sorted, then returns results in the original row order:

tidy(sales) >> mutate(
    running=order_by("sale_date", col("amount").cum_sum()),
    previous=with_order("sale_date", lag, "amount"),
    by="region",
)

Mutating joins accept dplyr-style safety controls:

orders = tidy({"order_id": [1, 2, 3], "customer_id": [10, 11, 10], "total": [25.0, 40.0, 15.0]})
customers = tidy({"customer_id": [10, 11], "name": ["Ana", "Ben"]})

orders >> left_join(
    customers,
    on="customer_id",
    relationship="many-to-one",
    unmatched="error",
    multiple="all",
    na_matches="never",
    keep=False,
)

relationship accepts one-to-one, one-to-many, many-to-one, or many-to-many; multiple accepts all, any, first, or last. Polars relationship and unmatched checks remain lazy and raise on collection.

Every frame-returning Phase 1–8 verb stays lazy on the Polars backend. pull, setequal, plotting, previews, and explicit collect are intentional materialization boundaries. Schema-dependent reshape operations may run a small metadata query as described above. slice_sample(weight_by=...), including replace=True, is supported on both backends. Group-context helpers and additional vector helpers remain future phases.

Performance controls

Grouped mutate() expressions automatically reuse embedded or repeated statistics. Expressions such as the following compute each group mean and standard deviation once on both backends; temporary columns never appear in the result:

features = {"segment": ["a", "a", "a", "b", "b"], "x": [1.0, None, 3.0, 10.0, 14.0]}

tidy(features) >> mutate(
    filled=coalesce(col("x"), mean("x", na_rm=True)),
    z=(
        coalesce(col("x"), mean("x", na_rm=True))
        - mean("x", na_rm=True)
    ) / std("x", na_rm=True),
    by="segment",
)

Project before a pandas/Arrow handoff without adding another pipeline verb:

# A model-ready table: one row per customer
result = tidy({
    "customer_id": [101, 102, 103],
    "segment": ["a", "b", "a"],
    "feature_a": [0.1, 0.4, 0.3],
    "feature_b": [1.0, 0.0, 1.0],
    "feature_c": [12.5, 9.0, 11.0],
})

matrix = result.collect(
    as_="pandas",
    columns=["customer_id", starts_with("feature_")],
    arrow_backed=True,
)

arrow_backed=True still returns a pandas DataFrame, but avoids copying Polars columns into NumPy buffers. Leave it off when a downstream library specifically requires NumPy-backed pandas dtypes.

distinct(..., maintain_order=True) preserves dplyr row order by default. Use maintain_order=False when output order is irrelevant and throughput is more important.

NumPy, Numba, and PyTorch

Build the matrix directly from the lazy pipeline and project away identifiers or string columns before materializing:

import numpy as np
from tidy3 import starts_with, to_numpy

features = result.to_numpy(
    columns=["feature_a", "feature_b", "feature_c"],
    dtype=np.float32,
    order="c",
    writable=True,
)

# Equivalent output boundaries
features = result.collect(as_="numpy", columns=starts_with("feature_"))
features = result >> to_numpy(columns=starts_with("feature_"))
features = np.asarray(result)  # all columns; materializes the lazy plan

Numba functions accept the returned array directly. For PyTorch, torch.from_numpy(features) shares the CPU array's memory, so request writable=True; use order="c" when a consumer requires C-contiguous input. The default is Fortran order because tidy3/Polars are columnar and it offers the best chance of avoiding a copy. Set allow_copy=False when an unexpected copy should be an error.

This is a host-memory bridge even when engine="gpu": Polars may execute the query on the GPU, but the NumPy result resides in CPU memory. A future DLPack bridge would be needed for a direct device-to-PyTorch handoff.

Benchmark vs datar

from tidy3 import bench
bench.run(rows=10_000_000)        # full pipeline; pip install datar datar-pandas for the datar row
bench.run_ops(rows=10_000_000)    # isolated verbs with each output boundary labelled

For the adoption-oriented suite, which covers everyday operations plus ML, event-history, customer aggregation, and join/filter/aggregate workflows:

python -m tidy3.bench_suite --rows 1000000 --repeat 5 --output pandas
python -m tidy3.bench_suite --rows 1000000 --repeat 5 --output pandas-arrow
python -m tidy3.bench_suite --rows 1000000 --repeat 5 --output native

# Compare Polars execution modes (GPU mode is strict: no silent CPU fallback)
python -m tidy3.bench_suite --rows 1000000 --repeat 5 --output native --polars-engine auto
python -m tidy3.bench_suite --rows 1000000 --repeat 5 --output native --polars-engine streaming
python -m tidy3.bench_suite --rows 1000000 --repeat 5 --output native --polars-engine gpu

# Ratio-based CI budgets; workloads under 10ms are ignored as noise-prone
python -m tidy3.bench_suite --rows 1000000 --repeat 5 --output native \
  --max-tidy-pandas-geo 1.25 --max-tidy-polars-geo 1.25 \
  --budget-min-ms 10

The default pandas output makes every engine return a NumPy-backed pandas DataFrame and therefore includes the Polars-to-pandas ML handoff. pandas-arrow still returns pandas but usually avoids that copy; native keeps results in Polars and isolates execution from conversion. Data generation, warm-up, garbage collection, and correctness validation are outside recorded times; every measured result is checked against raw pandas. The suite reports medians and rotates engine order between repetitions. --polars-engine accepts auto, streaming, and gpu; GPU benchmarking uses strict Polars GPU execution and stops if a query would fall back to CPU. Optional datar coverage remains in the smaller tidy3.bench benchmark as a backup comparison.

Apple-silicon laptop, 10M rows × 100 groups, filter→mutate→group_by→summarise→arrange:

engine	time	vs fastest
tidy3[polars]	40.6ms	1.0x
polars (raw lazy)	41.5ms	1.0x
pandas (raw)	60.1ms	1.5x
tidy3[pandas]	60.8ms	1.5x
datar[pandas]	166.3ms	4.1x

An isolated one-expression mutate is a useful boundary stress test because pandas Copy-on-Write makes the baseline unusually cheap. On the same laptop, 10M rows, median of 7 runs after 2 warm-ups:

execution and output boundary	time	vs raw pandas
tidy3[pandas] → pandas	5.0ms	1.0x
raw pandas → pandas	5.1ms	1.0x
tidy3[polars] → native Polars	10.4ms	2.1x
raw Polars → native Polars	10.7ms	2.1x
tidy3[polars] → Arrow-backed pandas	11.1ms	2.2x
datar[pandas] → pandas	11.3ms	2.2x
tidy3[polars] → NumPy-backed pandas	32.2ms	6.4x

This replaces the old 41.9ms (8.7x) cell, which combined Polars execution with a full NumPy conversion and presented the total as one engine number. The remaining 2.1x on this deliberately tiny operation is Polars engine cost: tidy3 tracks raw Polars within measurement noise. For a single cheap mutate followed immediately by NumPy pandas, use the pandas backend. For longer lazy pipelines, collect once at the end, project needed columns first, and prefer native or Arrow-backed output. Aggregations, joins, sorts, and full workflows are the adoption-relevant comparison in bench_suite.

Under %gpu, run the same benchmarks on the remote kernel. Install Polars GPU support there first, then use --polars-engine gpu; the comprehensive suite does not require datar.

R semantic-parity oracle

tests/test_r_oracle_parity.py compares every public frame verb with dplyr or tidyr, or assigns it to an explicit invariant/materialization category. The suite includes missing and empty inputs, persistent and transient grouping, categorical levels, duplicate names, and type coercion. Install R with dplyr, tidyr, and jsonlite, then run:

pytest -q tests/test_r_oracle_parity.py

If R is kept in a Pixi environment, point the suite at its manifest:

TIDY3_R_ORACLE_MANIFEST=/path/to/pixi.toml \
  pytest -q tests/test_r_oracle_parity.py

All supported verb contracts in the oracle are strict tests on both backends; there are no expected-failure parity cases. Random sampling and explicit materialization boundaries use deterministic invariants where byte-for-byte comparison with R would be inappropriate.

Examples

Local end-to-end prep for algorithms (no CRAFT required):

pip install -e ".[dev]"
python examples/prep_for_ml.py
python examples/prep_for_ml.py --torch   # if torch is installed

That script builds a tidy feature frame, materializes a NumPy matrix with to_numpy, optionally wraps it for PyTorch, and writes a plot3 scatter when plot3 is on the path.

Development

pip install -e ".[dev]"
python -m pytest -q

CI (GitHub Actions):

• Tests — pytest on Python 3.10–3.14 for every push/PR; optional R semantic oracle job installs dplyr/tidyr/jsonlite and runs the differential suite
• Performance budget — python -m tidy3.bench_suite geometric ratios vs raw pandas (see .github/workflows/). Experimental Python-callback workloads (e.g. group_modify) are timed but excluded from the adoption geo-mean.

On a machine without R, oracle tests skip automatically. To run them locally:

# after installing R + dplyr, tidyr, jsonlite
pytest -q tests/test_r_oracle_parity.py

Releases go to PyPI from a version tag; see docs/releasing.md.

Notes

• Grouped semantics are dplyr's: after group_by, mutate/filter/ slice_*/sample_n/head evaluate per group (Polars window .over). summarise aggregates per group.
• Display is self-contained: tables carry inline styles (no <style> block), so they render identically in local cells, republished %gpu output, and sslive exports. Under %gpu, bare polars DataFrames are restyled the same way (seed_tidy3_remote(style_polars=False) to opt out).
• Builtins are shadowed by design: injecting the API puts filter, slice, sum, min, max, any, and all into the notebook namespace. Use builtins.filter etc. when you need the Python originals.
• Plotting big remote data: aggregate remotely, then let plot3's own remote path pull the small result: %plot3 res.to_pandas() x=... y=....
• API maturity tiers (stable / growing / experimental) are listed under API maturity. Prefer the stable core for adoption and performance-sensitive work.

Why not datar?

datar’s pandas/Python wrappers struggle on large frames. tidy3 compiles verbs to a Polars Lazy plan and only materializes at the edge. Previews use LIMIT n.

License

MIT