tl;dr “Foo” and “bar” as metasyntactic variables were popularised by MIT and DEC, the first references are in work on LISP and PDP-1 and Project MAC from 1964 onwards. Many of these people were in MIT’s Tech Model Railroad Club, where we find the first documented use of “foo” in tech circles in 1959 (and … Read more
Yep, _ is a traditional name for “don’t care” (which unfortunately clashes with its use in I18N, but that’s a separate issue;-). BTW, in today’s Python, instead of: _,s = min( (len( values[s]), s) for s in squares if len(values[s]) > 1 ) you might code s = min((s for s in squares if len(values[s])>1), … Read more
_ has 3 main conventional uses in Python: To hold the result of the last executed expression in an interactive interpreter session (see docs). This precedent was set by the standard CPython interpreter, and other interpreters have followed suit For translation lookup in i18n (see the gettext documentation for example), as in code like raise … Read more