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Examples

Runnable demonstrations of one data problem each — config, input, and the exact transformation. Open any card for the full story; the View on GitHub button on each page links the complete files to run it yourself.

Real-world use cases

Real public datasets — each page cites its source and the documented problem it solves.

  • Chicago Business Licenses → Analytics Schema

    Turn the City of Chicago's raw Business Licenses export into a readable analytics CSV: cryptic status/type codes decoded to plain English, ISO dates, and an explicit marker for the (very common) missing application date.

  • JHU COVID-19 Wide → Long (unpivot)

    Reshape the Johns Hopkins COVID-19 confirmed-cases time series from its native wide layout (one column per day) into long/tidy rows (one row per country-date), using a single template.

  • Eurostat Population (bulk TSV) → Clean Per-Country Rows

    Turn one row of Eurostat's bulk demo_pjan download (population on 1 January) into a clean per-country row: dimensions unpacked into their own columns, year values stripped of their quality-flag suffixes, and the : missing-data marker turned into a real empty cell — all in one template.

  • French DVF Real-Estate → Analytics Schema

    Reshape France's official "Demandes de valeurs foncières" (DVF) raw real-estate transaction export into a clean analytics CSV with ISO dates, proper euro amounts, and a repaired postal code.

  • GTFS Stops → Self-Join (pre_pass + LOOKUP)

    Enrich every NYC-subway platform row with its parent station name — a value that lives on a different row of the same file — using bxp's pre_pass + LOOKUP.

  • HL7 v2 ADT Feed → Patient Roster

    Pull a flat patient roster (MRN, name, birth date, sex) out of a feed of HL7 v2 ADT messages — keeping only the PID segments, splitting the ^-delimited name components, and reformatting the birth date — with no HL7 parser library.

  • IMDb Title Basics → Catalog Row

    Reshape IMDb's public title.basics.tsv into a CSV catalogue row with normalised null markers, exploded genres, and a boolean adult column.

  • Inside Airbnb NYC Listings → Analytics Schema

    Reshape Inside Airbnb's public NYC scrape into an analytics CSV with short room-type codes, a regulatory-status column, and a visible sentinel for the redacted price field.

  • OpenNGC Sexagesimal Coordinates → Decimal Degrees

    Convert the celestial coordinates in the OpenNGC deep-sky catalogue from sexagesimal form — right ascension as HH:MM:SS.s (hours) and declination as ±DD:MM:SS.s — into decimal degrees, the form plotting libraries, GIS tools and cross-match services expect.

  • NOAA GHCN Daily → Metric Units

    Convert NOAA Global Historical Climatology Network daily records into a CSV with proper SI units (°C and mm) and a per-row consistency flag.

  • NYC Yellow Taxi Trips → Analytics Schema

    Convert raw NYC TLC Yellow Taxi trip records into an analytics-ready CSV with ISO timestamps, human-readable payment types, and a per-row data quality flag.

  • RÚIAN address points — a zipped CSV-per-municipality export

    The Czech state address register (RÚIAN) is published as a single ZIP holding one Windows-1250, semicolon-delimited CSV per municipality, all under a CSV/ folder inside the archive.

  • NYC Squirrel Census (JSON API) → Flat CSV

    Flatten the 2018 NYC Central Park Squirrel Census — published as a JSON array by a REST/Socrata API — into a tidy CSV, taking the union of keys across heterogeneous records, coercing native JSON booleans to text, skipping a nested geo object, and parsing a separator-less date, all in one template.

  • US Treasury Yield Curve (wide → long) + tenor mapping

    Melt the US Treasury's daily par-yield-curve CSV from its native wide layout (one column per maturity — 1 Mo, 2 Yr, … 30 Yr) into long/tidy rows (one row per date-tenor), converting the US date to ISO and mapping each maturity label to its length in months — all in one template.

Teaching — basic

Synthetic, minimal inputs that isolate one engine feature at a time.

  • Null Variants → Empty

    Fold every "no value" spelling — NULL, NA, N/A, n/a, None, "-" — into a single genuine empty cell, while leaving real values untouched.

  • Space-Grouped Thousands → Number

    Parse the continental-European number format — space-grouped thousands with a comma decimal, "1 234 567,89" = 1234567.89 — into a clean numeric value.

  • Timezone Functions — normalise to UTC, convert between zones

    Turn messy per-broker timestamps into clean UTC and derive zone facts with the four timezone builtins — TO_UTC, TZ_OFFSET, IS_DST, and TZ_CONVERT — all DST-aware, no external service.

  • Units-in-Cell → Number + Unit

    Split a measurement column that glues a number to its unit — 5.0 kg, 250 g, 1.5 L, 12 pcs — into a clean numeric amount and a separate unit column.

Teaching — intermediate

Synthetic examples combining a few features.

  • Accounting Negatives → Signed Decimals

    Normalise an accounting/bank/ERP export where negative amounts are written in parentheses — "(2,500.00)" means -2500 — and thousands are comma-grouped, into a clean signed-decimal column.

  • Boolean Variants → Canonical true/false

    Fold boolean columns written every which way — Yes/No, Y/N, 1/0, true/false, TRUE/T/F, mixed case — into a canonical true/false, with blanks and unrecognised junk left empty.

  • Fan-In Many Files → One Table (combined_output)

    Stack a folder of same-shape exports — one CSV per day/month — into a single combined table, in deterministic order, with no manual cat and no repeated header rows.

  • HubSpot Contacts → Salesforce Lead

    Convert a HubSpot Contacts CSV export into a Salesforce Lead Import CSV.

  • JSON Union → One CSV (heterogeneous keys)

    Merge several JSON exports whose objects carry different key sets into a single CSV with every column, where a key a record never had collapses to an empty cell.

  • Percent / Basis Points → Decimal Fraction

    Normalise a Rate column that mixes percent (2.5%), basis points (25 bps) and the odd already-decimal legacy value (0.03) into one consistent decimal fraction.

  • Price + Currency Split

    Split a single mixed-notation Price column — $12.99, 50.00 EUR, €3.50, 1,234.00 USD — into a clean numeric price and a separate currency code, using bxp's PRICE_VALUE / PRICE_CURRENCY builtins.

Teaching — advanced

Synthetic multi-pass pipelines, joins, and capstones.