CSV
Tailing and Following a CSV That Is Still Being Written
Follow a growing CSV with tail -f, skip the header, survive rotation with tail -F and read only complete lines, plus a Python follower and the buffering trap.
6 min read
Library
Everything you need to level up your coding skills.
YAML
Generating SQL From YAML Templates Safely With Bound Values
See an f-string builder turn a YAML job file into a dropped table, then fix it with bound values, quoted identifiers and an allow-list of tables.
6 min read
Excel
Rank Customers by Spend in Excel and SQL With Ties Handled
Rank customers by spend with RANK.EQ and sorted lists in Excel and with RANK, DENSE_RANK and ROW_NUMBER in SQL, including ties, top N and ranks per group.
7 min read
CSV
How Much Memory pandas Needs to Load a CSV File in 2026
pandas needed 3.9 GB of peak memory to load a 1.3 GB CSV, and 0.18 GB to keep two typed columns. Measure it yourself with memory_usage and a rule of thumb.
6 min read
XML
Moving From XML to JSON Gracefully Without Losing Meaning
Generic converters guess at lists, attributes and mixed text. Write a small mapping with explicit rules so the JSON stays predictable for every record.
6 min read
JSON
Checking a JSON Column Against a Schema in PostgreSQL
Enforce the shape of a PostgreSQL jsonb column with CHECK constraints, NOT VALID and jsonpath, including the NULL trap that lets a string id pass.
8 min read
CSV
Compressing CSV Files and Reading Them Without Unzipping
Compress a CSV with gzip or zstd and read it directly with zcat, pandas, DuckDB or Python: 130 MB became 34 to 43 MB and no unzipped copy was needed.
6 min read
Excel
Running Total of Monthly Sales Both Ways in Excel and SQL
Build a monthly running total in Excel with expanding ranges, SUMIFS and SCAN, and in SQL with a window function, including ties and resets.
7 min read
CSV
Sampling Random Rows From a Huge CSV Without Loading It
Take a random sample of a 1.3 GB CSV with shuf, awk, DuckDB or a seek: all run in seconds, but line-based samples break rows that contain a newline.
6 min read
XML
Converting JSON to XML With Sensible Element Names
JSON keys can be any string and XML names cannot. Make legal names from spaces and leading digits, write arrays as repeated elements, and mark null.
7 min read
YAML
Generating Table Schemas From YAML Definitions Safely
Generate CREATE TABLE statements from a YAML definition, quote identifiers so order and group work, and run the same DDL on PostgreSQL, SQLite and DuckDB.
6 min read
Excel
Joining Two Sheets on Two Keys in Excel and in SQL
Join two sheets on two keys in Excel with XLOOKUP, SUMIFS or Power Query, and in SQL with a two-column join, handling duplicates, NULLs and missing matches.
6 min read
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