Data Transform (dt)

A fast, readable data transformation tool for working with tabular data. Built with Rust and Polars.

Why dt?

Clearer than pandas, faster than awk, zero setup.

• Readable syntax: Named operations and clear pipelines
• Polars-powered: Parallel processing, optimized queries, columnar operations
• Single binary: No Python environments, no dependencies to manage
• Interactive REPL: See results after each transformation
• Multi-file operations: Clean syntax for joins and lookups

Installation

# Shell installer (macOS/Linux)
curl --proto '=https' --tlsv1.2 -LsSf https://github.com/system0x7/dt/releases/latest/download/data-transform-installer.sh | sh

# Cargo
cargo install data-transform

# From source
cargo install --git https://github.com/system0x7/dt

Quick Start

Interactive REPL

$ dt
>> data = read('sales.csv')
Stored: data (7 rows × 4 cols)
[Table: 7 rows × 4 cols]
shape: (5, 4)
┌──────────┬─────────────┬────────┬──────────┐
│ product  ┆ category    ┆ price  ┆ quantity │
│ ---      ┆ ---         ┆ ---    ┆ ---      │
│ str      ┆ str         ┆ f64    ┆ i64      │
╞══════════╪═════════════╪════════╪══════════╡
│ Laptop   ┆ Electronics ┆ 899.99 ┆ 5        │
│ Mouse    ┆ Electronics ┆ 24.99  ┆ 120      │
│ Desk     ┆ Furniture   ┆ 299.0  ┆ 8        │
│ Chair    ┆ Furniture   ┆ 159.99 ┆ 15       │
│ Keyboard ┆ Electronics ┆ 79.99  ┆ 45       │
└──────────┴─────────────┴────────┴──────────┘
... 2 more rows

>> data = data | filter(price > 100)
Stored: data (5 rows × 4 cols)
[Table: 5 rows × 4 cols]
shape: (5, 4)
┌───────────┬─────────────┬────────┬──────────┐
│ product   ┆ category    ┆ price  ┆ quantity │
│ ---       ┆ ---         ┆ ---    ┆ ---      │
│ str       ┆ str         ┆ f64    ┆ i64      │
╞═══════════╪═════════════╪════════╪══════════╡
│ Laptop    ┆ Electronics ┆ 899.99 ┆ 5        │
│ Desk      ┆ Furniture   ┆ 299.0  ┆ 8        │
│ Chair     ┆ Furniture   ┆ 159.99 ┆ 15       │
│ Monitor   ┆ Electronics ┆ 349.99 ┆ 12       │
│ Bookshelf ┆ Furniture   ┆ 189.0  ┆ 6        │
└───────────┴─────────────┴────────┴──────────┘

>> data = data | mutate(total = price * quantity)
Stored: data (5 rows × 5 cols)
[Table: 5 rows × 5 cols]
shape: (5, 5)
┌───────────┬─────────────┬────────┬──────────┬─────────┐
│ product   ┆ category    ┆ price  ┆ quantity ┆ total   │
│ ---       ┆ ---         ┆ ---    ┆ ---      ┆ ---     │
│ str       ┆ str         ┆ f64    ┆ i64      ┆ f64     │
╞═══════════╪═════════════╪════════╪══════════╪═════════╡
│ Laptop    ┆ Electronics ┆ 899.99 ┆ 5        ┆ 4499.95 │
│ Desk      ┆ Furniture   ┆ 299.0  ┆ 8        ┆ 2392.0  │
│ Chair     ┆ Furniture   ┆ 159.99 ┆ 15       ┆ 2399.85 │
│ Monitor   ┆ Electronics ┆ 349.99 ┆ 12       ┆ 4199.88 │
│ Bookshelf ┆ Furniture   ┆ 189.0  ┆ 6        ┆ 1134.0  │
└───────────┴─────────────┴────────┴──────────┴─────────┘

>> data = data | select(product, category, total)
Stored: data (5 rows × 3 cols)
[Table: 5 rows × 3 cols]
shape: (5, 3)
┌───────────┬─────────────┬─────────┐
│ product   ┆ category    ┆ total   │
│ ---       ┆ ---         ┆ ---     │
│ str       ┆ str         ┆ f64     │
╞═══════════╪═════════════╪═════════╡
│ Laptop    ┆ Electronics ┆ 4499.95 │
│ Desk      ┆ Furniture   ┆ 2392.0  │
│ Chair     ┆ Furniture   ┆ 2399.85 │
│ Monitor   ┆ Electronics ┆ 4199.88 │
│ Bookshelf ┆ Furniture   ┆ 1134.0  │
└───────────┴─────────────┴─────────┘

>> data | write('revenue.csv')
Written: revenue.csv (5 rows × 3 cols)

The REPL shows the table after each operation, letting you verify transformations before saving.

One-liner

   dt "read('data.csv') | filter(price > 100) | write('output.csv')"

From script file

dt -f transform.dt

Example: Multi-file lookup

# Load reference data
pops = read('pops.txt', header=false)
ref = read('reference.ind', header=false)
fam = read('reference.fam', header=false)

# Filter and join
keep = ref | filter($3 in pops)
result = fam | filter($2 in keep) | select($1, $2)

# Save results
result | write('output.tsv')  # .tsv extension auto-uses tab delimiter

Core Features

Column Selection

select($1, $2, $3)           # By position (1-based)
select($1..$5)               # Range (inclusive)
select(name, age, email)     # By name
select($1 as id)             # With renaming
drop($3..$7)                 # Remove columns

Filtering & Sorting

filter(age > 30)
filter(name == "Alice")
filter($3 in populations)
sort(age desc)
distinct(user_id)

Transformations

mutate(total = price * quantity)
mutate(full_name = first + " " + last)
mutate(domain = split(email, '@')[1])
mutate(label = lookup(labels, id, on='id', return='name'))

String Operations

mutate(clean = replace(text, 'old', 'new'))
mutate(parts = split(id, ':')[0])
mutate(combined = $1 + ':' + $2)

Renaming

rename(old_name -> new_name)
rename_all(replace('_', '-'))
rename_all('PC' + 1..50)     # PC1, PC2, ..., PC50

Multi-file Operations

# Load reference table
labels = read('labels.csv')

# Lookup values (single-line)
data = read('samples.csv') | mutate(population = lookup(labels, sample_id, on='id', return='pop'), region = lookup(labels, sample_id, on='id', return='region'))

# Or split at pipe boundaries for readability
data = read('samples.csv') |
	mutate(population = lookup(labels, sample_id, on='id', return='pop'), region = lookup(labels, sample_id, on='id', return='region'))

Documentation

See REFERENCE for complete syntax and examples.

Supported Formats

• JSON (.json) - Structured JSON data
• Parquet (.parquet) - Columnar format

Delimited text files - Delimiter auto-detected for any file:

• .csv - Defaults to comma, auto-detects if ambiguous
• .tsv - Defaults to tab, auto-detects if ambiguous
• Any other extension (.txt, .dat, .psv, etc.) - Auto-detects delimiter

Auto-detection analyzes file content and identifies: comma, tab, pipe, semicolon, or space.

Override auto-detection if needed:

read('data.txt', delimiter=' ')
read('data.psv', delimiter='|')

Performance

Built on Polars, dt provides:

• Parallel processing using all CPU cores
• Columnar memory layout for cache efficiency
• Query optimization and lazy evaluation
• Type-aware operations

For typical data transformation tasks, dt is 5-10x faster than awk while being significantly more readable.

REPL Commands

• .help - Show help
• .schema - Show current table schema
• .vars - Show stored variables
• .history - Show operation history
• .undo [n] - Undo operations
• .clear - Clear current state
• .exit - Exit REPL

License

MIT