On 08/14/2017 08:25 PM, Larry Hudson wrote:
[snip]
Here is my attempt to clarify the situation with some ascii graphics.
(Well, not ascii, but utf-8 box-drawing characters — I hope they come through
ok.
And, of curse, it won't display properly with a proportional font.)
The left side is the program lines, and the right side tries to show the way Python implements
the name binding to the data in memory. (But I abbreviated the long assignment line,
alist[0],alist[1],alist[2]=3,6,9 to <assignment>)
Program line Variable bound to memory
=========== Initial assignment ============
ss = [1, 2, 3] ss ───> [1, 2, 3]
=============== test() code ===============
def test(alist): ss ─┬─> [1, 2, 3]
alist ─┘
---------------------------------------------
alist = [3, 6, 9] ss ───> [1, 2, 3]
alist ───> [3, 6, 9]
---------------------------------------------
return ss ───> [1, 2, 3]
alist <Garbage collected>
=============== test1() code ==============
def test1(alist): ss ─┬─> [1, 2, 3]
alist ─┘
---------------------------------------------
<assignment> ss ─┬─> [3, 6, 9]
alist ─┘
---------------------------------------------
return ss ───> [3, 6, 9]
alist <Garbage collected>
=============== test2() code ==============
def test2(alist): ss ─┬─> [1, 2, 3]
alist ─┘
---------------------------------------------
<assignment> ss ─┬─> [3, 6, 9]
alist ─┘
---------------------------------------------
alist = [30, 60, 90] ss ───> [3, 6, 9]
alist ───> [30, 60, 90]
---------------------------------------------
return ss ───> [3, 6, 9]
alist <Garbage collected>
This needs a minor clarification to the test1 example, plus I want to emphasize that the
assignment here is through the alist variable.
=============== test1() code ==============
def test1(alist): ss ─┬─> [1, 2, 3]
alist ─┘
---------------------------------------------
<assignment> ss ─┬─> [3, 6, 9]
alist ─┘
---------------------------------------------
return ss ───> [3, 6, 9]
alist <Discarded> There is nothing to garbage
collect here.
--
-=- Larry -=-
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