JSON
Using JSON Schema Enums Formats and Patterns Correctly
Where Python and Node disagree on JSON Schema formats and patterns: email, uri, hostname, digits, trailing newlines, plus exact enum and const behavior.
6 min read
Library
Everything you need to level up your coding skills.
XML
Parsing Tax Style E Invoices and Checking the Totals
Read a UBL style invoice with namespaced lines, recompute each line, sum the net amounts and compare the tax rounded per line with the tax per rate group.
6 min read
Excel
Date Formulas for Month Ends and Business Days in Excel
Excel date formulas for month starts and ends, adding months, business days with holidays, fiscal years and age, with the edge cases that break them.
7 min read
CSV
Converting CSV to SQL INSERT Statements the Safe Way
Generate INSERT statements from a CSV without breaking on O'Neil or running a DROP TABLE hidden in a value. Batches of 1,000 loaded 193,708 rows in 1.6 s.
13 min read
YAMLGuide
YAML in Data Engineering Workflows and Where It Fits
Where YAML belongs in a data platform: tool config, contracts, schemas, pipelines, tests and docs, with a tested end to end example and the limits of each.
17 min read
Excel
LET and LAMBDA for Readable Formulas in Excel Workbooks
Use LET to name values and LAMBDA to define reusable functions so long Excel formulas become readable, faster and easier to review, with portability notes.
6 min read
CSV
Converting JSON to CSV When the Data Is Nested With Arrays
Flatten nested JSON to CSV with pandas, Python or DuckDB: dotted columns, a row per array item, the order that vanishes and arrays written as Python text.
10 min read
XML
Reading a Medical Style HL7 CDA Document Safely With lxml
Extract the patient id and measurements from a synthetic CDA clinical document with a namespace map, handle nullFlavor and disable entity resolution.
6 min read
JSON
Validating Arrays and Nested Objects With JSON Schema
Validate arrays of objects, tuples and deep nesting with JSON Schema: items, prefixItems, contains, uniqueItems and error paths, tested in Python.
6 min read
PostgreSQL
Tuning PostgreSQL for SSDs With random_page_cost and More
Tune PostgreSQL for SSDs: lower random_page_cost, set effective_io_concurrency, check changed plans, use per tablespace values and keep scans that win.
7 min read
CSV
Converting Excel to CSV Without Losing Leading Zeros
pandas turned a text cell 02134 into 2134 and in2csv did too; qsv kept it. A number formatted 00000 loses its zeros everywhere unless you rebuild them.
10 min read
Excel
TEXTSPLIT TEXTJOIN and Text Cleanup Formulas That Work
Use TEXTSPLIT, TEXTJOIN, TEXTBEFORE and TEXTAFTER with TRIM, CLEAN and SUBSTITUTE to clean text in Excel, with fallbacks for older versions.
6 min read
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