On Mon, 29 Aug 2022 at 15:54, Jach Feng <jf...@ms4.hinet.net> wrote: > > Richard Damon 在 2022年8月29日 星期一上午10:47:08 [UTC+8] 的信中寫道： > > On 8/27/22 7:42 AM, Mark Bourne wrote: > > > Jach Feng wrote: > > >> I have two files: test.py and test2.py > > >> --test.py-- > > >> x = 2 > > >> def foo(): > > >> print(x) > > >> foo() > > >> > > >> x = 3 > > >> foo() > > >> > > >> --test2.py-- > > >> from test import * > > >> x = 4 > > >> foo() > > >> > > >> ----- > > >> Run test.py under Winows8.1, I get the expected result: > > >> e:\MyDocument>py test.py > > >> 2 > > >> 3 > > >> > > >> But when run test2.py, the result is not my expected 2,3,4:-( > > >> e:\MyDocument>py test2.py > > >> 2 > > >> 3 > > >> 3 > > >> > > >> What to do? > > > > > > `from test import *` does not link the names in `test2` to those in > > > `test`. It just binds objects bound to names in `test` to the same > > > names in `test2`. A bit like doing: > > > > > > import test > > > x = test.x > > > foo = test.foo > > > del test > > > > > > Subsequently assigning a different object to `x` in one module does > > > not affect the object assigned to `x` in the other module. So `x = 4` > > > in `test2.py` does not affect the object assigned to `x` in `test.py` > > > - that's still `3`. If you want to do that, you need to import `test` > > > and assign to `test.x`, for example: > > > > > > import test > > > test.x = 4 > > > test.foo() > > > > > Yes, fundamental issue is that the statement > > > > from x import y > > > > makes a binding in this module to the object CURRECTLY bound to x.y to > > the name y, but if x.y gets rebound, this module does not track the changes. > > > > You can mutate the object x.y and see the changes, but not rebind it. > > > > If you need to see rebindings, you can't use the "from x import y" form, > > or at a minimum do it as: > > > > > > import x > > > > from x import y > > > > then later to get rebindings to x.y do a > > > > y = x.y > > > > to rebind to the current x.y object. > > > > -- > > Richard Damon > Yes, an extra "import x" will solve my problem too! Sometimes I am wondering > why "from x import y" hides x? hum...can't figure out the reason:-) >
"from x import y" doesn't hide x - it just grabs y. Python does what you tell it to. :) ChrisA -- https://mail.python.org/mailman/listinfo/python-list
