Editor's pick
CSVGuide
Opening CSV Files in Excel and Sheets Without Damage
How to open, edit and save CSV files in Excel, Google Sheets and LibreOffice without losing zeros, digits, dates or accents: imports, settings, traps.
17 min read
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Everything you need to level up your coding skills.
CSV
Doing a Three Way Merge of CSV Edits by Key and by Cell
Merge two people's edits of a CSV against a common base: git merge-file conflicts when both touch a row, merging by key and cell resolves different cells.
6 min read
CSV
Keeping a CSV Sorted So Diffs Stay Small in Version Control
Keep a CSV sorted by its key so a one-row change is a one-line diff: sort the body not the header, use byte order and numeric keys, and sort in the writer.
6 min read
CSV
Using git diff Sensibly on a CSV File With Word Diff
Make git diff readable for a CSV: word diff on commas, a textconv that aligns columns, a sorted file with one record per line and a trailing newline.
6 min read
CSV
Calculating Month Over Month Growth From a CSV in SQL
Compute month over month growth with lag(): revenue of 46.50, 202.00 and 382.00 grew 334.4% and then 89.1%. Partial months, gaps and a zero base need care.
6 min read
CSV
Filling Gaps in a CSV Time Series With SQL and DuckDB
Find and fill missing days in a CSV time series: build a calendar with range(), left join the data and choose zero, carry-forward or interpolation.
7 min read
CSV
Joining Two CSV Files on a Messy Key Without Losing Rows
Join two CSVs on a messy key: a strict join matched 1 of 4 orders, a normalized key matched 3, and an anti-join listed the rest. Check counts and duplicates.
6 min read
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
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
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
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
CSV
Counting Lines in a Multi Gigabyte CSV Quickly and Correctly
wc -l counts a 1.3 GB CSV in under a second and is 9,856 rows off, because quoted newlines add lines. DuckDB counts records in 1 s; csv.reader takes 15 s.
6 min read
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