PEP 572: Assorted fixes suggested by Rob Cliffe

[gvanrossum]

No description provided.

[tim-one]

Ick - this example seems wholly contrived. How about keeping the original # A more explicit ... comment but changing the example to match it?

Before:
    for line in iter(somefile.readline, ""):
        process(line)
After:
    while line := somefile.readline():
        process(line)

Maybe that just especially appeals to me because I can never remember what 2-arg iter() does ☹️

[ncoghlan]

The problem with file based examples is that they typically collapse down to for line in somefile: ... in real code. It really is only in cases where native iteration support isn't available for some reason that you need to resort to the loop-and-a-half pattern instead.

[giampaolo]

Another real-world example involving files is:

while chunk := somefile.read(8192):
     process(chunk)

It doesn't belong to this paragraph though (I'm merely mentioning it)

[tim-one]

@giampaolo, I think that would be an excellent example to replace the one here! The clumsy 2-arg iter way of spelling that is

for chunk in iter((lambda: somefile.read(8192)), ""):

[gvanrossum]

Adding this now.

[tim-one]

s/all operators/all other operators/ ? That change would seem to be in the spirit of the OP's complaints.

[Rosuav]

According to the table at https://docs.python.org/3/reference/expressions.html#operator-precedence the comma is not an operator in Python. It's always a syntactic construct. I suppose you could argue that it's an operator taking two or more operands, and returns a tuple containing them, but that's pushing the definition a bit.

[tim-one]

Right, comma isn't "really" an operator, but pretending otherwise is common in explanatory text. The idea is that the RHS of := goes on until you hit a comma or unmatched right paren/bracket/brace. The fiction is useful because specifying the actual grammar is full of details that - while necessary for the implementation - aren't really illuminating.

[Rosuav]

Okay. Then let's go with "other"; it'll be technically correct in that "all other operators" means "everything except :=", and colloquially correct in that it means "everything except the comma".

[gvanrossum]

The "all other operators" change is already part of #718.

[tim-one]

Added 2 comments, and that's it.