On Sun, May 27, 2018 at 9:40 AM, Thomas Jollans <t...@tjol.eu> wrote: > On 27/05/18 01:19, Mike McClain wrote: >> In their discussion of 'List replication operator' >> Steven D'Aprano and Ben Finney used these '_' and '__'. >> Steve said, "[[] for _ in range(5)]". >> Ben said, "[ [] for __ in range(5) ]". >> >> These aren't listed separately in the index, where might I find >> written discussion of these? > > There's nothing special about _, it's just a possible name of a > variable, albeit a very short and entirely uninformative one. Normally, > it's not something you'd actually want to name a variable, of course. > > As such, _ has become an idiomatic name for dummy variables, i.e. > something you use when syntax requires you to give a variable name, but > you don't actually want one (probably because you're throwing the > variable away). This mostly happens in generator expressions/list > comprehensions.
Yes, and also in stand-alone 'for' loops where you don't care about the iteration variable: for _ in range(3): datafile.skipline() The only actual significance of this name is that the interactive interpreter will stash the result of the previous expression in that variable. >>> 6 * 7 42 >>> _ + 1 43 Other than that, it is simply an ordinary name, but one that has some conventions attached to it. ChrisA -- https://mail.python.org/mailman/listinfo/python-list