YAML
Naming Keys Consistently in YAML Config Files Everywhere
Pick one key style, enforce it with a JSON Schema pattern and fix old files with a yq command that renames every key. Real output for each step.
6 min read
Library
Everything you need to level up your coding skills.
Excel
Fixing the Python xlrd Error Excel xlsx Not Supported
Fix XLRDError Excel xlsx file not supported in pandas and Python: xlrd 2 reads only old xls files, so install openpyxl and pick the right engine.
6 min read
CSV
Using the Python csv Module for Reading Files Line by Line
Read CSV in Python with csv.reader: open with newline='', handle quoted commas and multi-line fields, set the dialect, and stream millions of rows.
8 min read
JSON
Building JSON Output With JSON_OBJECT and JSON_ARRAYAGG
Build nested JSON from MySQL tables with JSON_OBJECT and JSON_ARRAYAGG, and handle booleans, ordering, empty results and join fan-out.
7 min read
PostgreSQLGuide
Reading EXPLAIN ANALYZE Output in PostgreSQL Step by Step
Read EXPLAIN ANALYZE output in PostgreSQL: plan tree, cost, rows and loops, scan and join nodes, BUFFERS, sorts, estimates and a way to find the slow step.
18 min read
XML
Disabling DTDs and External Entities in Java and Python
Parser settings that stop XXE in Java and Python, tested on one file: which Java features block it, what each error says, and the lxml options.
7 min read
Editor's pick
CSVGuide
Reading and Writing CSV Files in Python the Right Way
A working guide to CSV in Python: csv module, DictReader, pandas, polars and DuckDB measured on 2,000,000 rows, plus the encoding, quoting and type rules.
22 min read
Excel
Excel Cannot Open the File Because the File Is Corrupt
Recover data from an Excel file that will not open: test the zip, try Open and Repair, extract sheet XML by hand and read what is left with Python.
7 min read
CSV
Writing Query Results Back Out to CSV With DuckDB COPY
Export a DuckDB query to CSV with COPY. Control the delimiter, NULL text, quoting, date format and compression, and split output into one file per value.
9 min read
YAML
Comments That Help the Next Person Reading Your YAML
What to write in YAML comments, what to leave out and how to lint comment style. Includes yamllint output for spacing and indentation, and what tools drop.
6 min read
JSON
Searching Values Inside a MySQL JSON Array Efficiently
MEMBER OF, JSON_CONTAINS, JSON_OVERLAPS and JSON_SEARCH compared on real tables, with a multi-valued index, and the matching rules for numbers and strings.
8 min read
Excel
Fixing Excel Found Unreadable Content After a Script Export
Fix the Excel message about finding a problem with some content after a script export, with the usual causes, how to read the repair log and how to bisect.
7 min read
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