Re: scared about refrences...


Marc 'BlackJack' Rintsch wrote:
In <1162236136.367603.165180@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, SpreadTooThin
wrote:

I'm really worried that python may is doing some things I wasn't
expecting... but lets see...

Expect that Python never copies something if don't ask explicitly for a
copy.

if I pass a list to a function def fn(myList):

and in that function I modify an element in the list, then does the
callers list get modied as well.

def fn(list):
list[1] = 0

myList = [1, 2, 3]
print myList
fn(myList)
print myList

[1,2,3]
[1,0,3]

How can I avoid this? In this case this is a really simplified example
but the effects are the same...

In this case:

def fn(lst):
lst = list(lst)
lst[1] = 0


How do I specify or create deep copies of objects that may contain
other objects that may contain other object that may contain other
objects....

See the `copy` module especially `copy.deepcopy()`.


This appears to be the right thing to do to me.. (but what do I know?)
I tried this which more closely resembles my project but this doesn't
work:

import array
import copy

class test:
def __init__(self):
self.a = array.array('H', [1, 2, 3])
self.b = ['a', 'b', 'c']

def dump(self):
print self.a, self.b

t = test()
t.dump()

def testit(x):
t = copy.deepcopy(x)
t.a[1] = 0
t.b[1] = 0

testit(t)

t.dump()

.

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