On 25/11/2014 11:40, Steven D'Aprano wrote:
PANDEY2 Archana (MORPHO) wrote:
Hello
I hereby would like to share the problem I have found regarding python
list implementation:-
As per python documentation python list is mutable data object.
That problem I found with the list is that is behaves differently when we
use '+=' and '+' '=' operators separately. For example-
a=a+1 and a +=1 both behave in same way for all data types except python
list
`a += b` is only *approximately* the same as `a = a+b`. The documentation
says:
An augmented assignment expression like x += 1 can be rewritten as x = x + 1
to achieve a similar, but not exactly equal effect. In the augmented
version, x is only evaluated once. Also, when possible, the actual
operation is performed in-place, meaning that rather than creating a new
object and assigning that to the target, the old object is modified
instead.
https://docs.python.org/2/reference/simple_stmts.html#augmented-assignment-statements
Please find the attached module and execute it on windows python32, See
the difference in output.
I cannot see the attached module. Did you forget to attach it, or did your
mail server delete it?
http://bugs.python.org/file37269/Operator_bug_python.py
a=[1,2,3]
b=a
b+=[4,5]
print(a)
print(b)
x=[1,2,3]
y=x
y=y+[4,5]
print(x)
print(y)
I know that you can explain it better than I can :)
--
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.
Mark Lawrence
--
https://mail.python.org/mailman/listinfo/python-list
