The first public release of Python happened on February 20, 1991, when Guido van Rossum posted version 0.9.0 to the alt.sources newsgroup on Usenet. In his own brief timeline of Python’s history, van Rossum lists the event plainly: “February 20, 1991 - 0.9.0 (released to alt.sources).”
Posting to alt.sources meant sharing the full source code with anyone reading the newsgroup, an early form of open distribution before the term “open source” was in common use. It put a working interpreter into the hands of a worldwide audience of programmers at no cost.
The same timeline records that implementation had only started in December 1989, so this release came a little over a year after van Rossum first began coding the language. He cautions that the earliest dates are approximate, since he did not consistently log every step at the time.
This single Usenet post marks the beginning of Python’s public life. From this small release grew a language that would, over the following decades, become one of the most widely used in software, data science, and artificial intelligence.