Publishing archive
Wednesday
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| 21 | 22 | 23 | 24 | 25 | 26 | 27 |
| 28 | 29 | 30 |
The highlighted days are the ones with something published; those are clickable.
IT
The twenty-fourth lesson of the Python course. The pandas module opens with the question it ought to open with: is the library worth it. A measurement answers, not belief. Where pandas is forty times faster, where it is merely twice, where it loses to an ordinary loop, what the memory costs — and the rule for when a table is needed.
IT
The twenty-third lesson of the Python course. A program that works through the night without you: arguments instead of editing the source, a journal with levels instead of `print`, a lock against two runs at once, and the exit code — the one thing the scheduler actually reads. Plus cron, launchd and systemd.
IT
The twenty-second lesson of the Python course. The database does the counting: `GROUP BY` gives one row per currency, `JOIN` brings the names from a second table, and a month is a group made of the first seven characters of the date. Plus the trap: over an empty answer `avg` returns `None` rather than zero.
IT
The twenty-first lesson of the Python course. A database instead of a file: a row is added, yesterday's stay, and running the same day again makes no duplicates. Plus two measured traps: a value glued into a query returned the whole table instead of one currency, and closing without a `commit` lost the row.
IT
The twentieth lesson of the Python course. Politeness to somebody else's server is three concrete things: a timeout, so you do not wait for ever; a retry with the pause doubling, so you do not hit what is already down; and a cache, so you do not ask twice. Measured on a server of our own: four readings, one request.
IT
The nineteenth lesson of the Python course. The same answer from the National Bank, read by a parser this time: 39 currencies, the rate taken by the name of a tag rather than by cutting a string. Plus two traps: `find` returns `None` for a tag that is not there, and a tag in a namespace is not found by its short name at all.
IT
The eighteenth lesson of the Python course. A request to the National Bank: 200, `text/xml`, 11,407 bytes — and those are `bytes`, not a string. Plus the difference that breaks error handling: `HTTPError` means the server said no, `URLError` means there was no answer at all.
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The seventeenth lesson of the Python course. The digest has grown into one long file, and it is time to lay it out under names. `import` runs somebody else's file whole, `__name__` tells a module from the file that was started, and your own `csv.py` beside the program quietly replaces the standard one.
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The sixteenth lesson of the Python course. A hundred thousand squares take almost four megabytes as a list and 376 bytes as a generator — measured, with every number counted in. The difference is not in how you count them but in when the values appear. Plus the mistake that matters: a generator is good for one pass, and the second one quietly gives you nothing.
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The fifteenth lesson of the Python course. Of the five names in the list only four are different: a set swallows the repeat without a word. In exchange, three questions about two exports take three signs: `&` for what is in both, `-` for what is gone, `|` for all of it. Plus `{}` is an empty dictionary, not an empty set.
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The fourteenth lesson of the Python course. There are 45 days between the 15th of January and the 1st of March, and `timedelta` counts them, not you. Plus two traps: `01.02.2026` parses under two formats without an error — as January and as February — and a naive time cannot be taken from an aware one, which Python says outright.
