semantics of open(buffering=-1) ?

[Skaperen]

the library reference manual shows for open() that the keyword argument buffering= has a default value of -1. it does not explain what that means or does. is it a default indicator like None usually is?

[ndc85430]

The docs do say what happens when no value is passed for buffering, i.e. what the default behaviour is (which is what -1 corresponds to). The great thing about Python being open source is that you can go look at the source - it is left as an exercise for you to find the source for open and see what it does with that argument.

[Skaperen]

then, what is the point of there being that document if the source can be used? i think Python would not be as popular as it is if everyone needed to read the source to know how it all worked? source is good, but not for this.

[ndc85430]

Well the docs do tell you what the default behaviour is and that buffering should be an integer, which is really about as much as you need to know as a user. If you actually care why the default is -1 instead of None then yeah, you can look at the source to see what it's doing.

[Skaperen]

back when i coded in C, -1 was often used as "assume nothing" value, even where i could have done that with 0. getting an answer to "why?" probably does need to go to source. a useful document would be "Python Tricks and Hints". it would tell programs a lot of ways to make things work, including telling when using -1 or -1.0 works out better than None. i'm curious, but not urgently so. i'll probably look at the source next year.