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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I would like to confirm my understanding of copying and its
implications.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>A shallow copy builds only a new outer shell and leaves the
inner references unchanged. <span style='mso-spacerun:yes'> </span>If the
outer object is immutable, then a copy might as well be the original object. So,
in the copy module, the copy function for tuples should just return the
original object (the function looks like it does more but actually does return
itself). And, since a <span class=SpellE>frozenset</span> is immutable, its
copy function should also just return self.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The point of a <span class=SpellE>deepcopy</span> is to
replace each sub-component (at every nesting level) that could possibly change.
<span style='mso-spacerun:yes'> </span>Since sets can only contain
hashable objects which in turn can only contain hashable objects, I surmise
that a <span class=SpellE>shallowcopy</span> of a set would also suffice as its
<span class=SpellE>deepcopy</span>.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>IOW:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span>For <span
class=SpellE>frozensets</span><span class=GramE>,<span
style='mso-spacerun:yes'> </span><span class=SpellE>shallowcopy</span></span>
== <span class=SpellE>deepcopy</span> == self<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><span style='mso-spacerun:yes'> </span>For sets,
<span class=SpellE>shallowcopy</span> == <span class=SpellE>deepcopy</span> == <span
class=GramE>set(</span>list(self))<span style='mso-spacerun:yes'>
</span># done with <span class=SpellE>PyDict_Copy</span>()<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Raymond Hettinger<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
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