On Tue, Jun 04, 2019 at 11:37:23PM +0000, nathan tech wrote:
> globals.py:
>
> feeds={}
> blank_feed={}
> blank_feed["checked"]=1
> blank_feed["feed"]=0
That is more easily, and better, written as:
feeds = {}
blank_feed = {"checked": 1, "feed": 0}
> main file:
>
> import globals as g
> # some code that loads a feed into the variable knm
Do you mean something like this? If so, you should say so.
knm = "some feed"
> g.feeds[link]=g.blank_feed;
What's "link" here? And there is no need for the semi-colon.
> g.feeds[link]["feed"]=knm
Right... what the above line does is *precisely* the same as
g.blank_feed["feed"] = knm
Follow the program logic. I'm inserting 1970s BASIC style line numbers
to make it easier to discuss the code, remember that you can't actually
do that in Python.
10: g.feeds[link] = g.blank_feed
20: g.feeds[link]["feed"] = knm
Line 10 sets g.feeds[link] to the dict "blank_feed". *Not* a copy: you
now have two ways of referring to the same dict:
"g.blank_feed" and "g.feeds[link]"
both refer to the one dict, just as "Nathan" and "Mr Tech" are two ways
of referring to the same person (you).
So line 20 does this:
- look for the name "g", which gives the "globals.py" module;
- inside that module, look for the name "feeds", which gives
the "feeds" dict;
- look inside that dict for the key "link" (whatever value
that currently holds), which by line 10 has been set to
the same dict "blank_feed".
- inside the blank_feed dict, set key "feed" to "knm".
> #in the below code, the variable link has a different value:
> # load a feed into the variable r
Something like this?
r = "a different feed"
> g.feeds[link]=g.blank_feed
Now you have *three* ways of naming the same dict:
"g.blank_feed", "g.feeds[link]", "g.feeds[different_link]"
but they all point to the same dict.
> g.feeds[link]["feed"]=r
>
>
> Now at this point, python would set the first loaded feed to the same
> thing as the second loaded feed. It also set g.blank_feed to the second
> feed, as well.
No, there is only one feed in total. You just keep updating the same
feed under different names.
> I replaced the last three lines with this:
>
> # load a feed into the variable r
> g.feeds[link]=g.blank_feed;
> g.feeds[link]["feed"]=r
>
> And it works.
I don't see any difference between the replacement code and the original
code. The code you show does exactly the same thing.
> but why does it work?
>
> Why does that semi unlink all the variables?
Semi-colon?
It doesn't. You must have made other changes as well, semi-colons don't
have any runtime effect. They are *purely* syntax to tell the parser to
seperate multiple statements on one line.
--
Steven
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