Dear StevenThank you.  
I am clear now.Padmanabhan

     On Saturday, June 6, 2015 5:12 PM, Steven D'Aprano <report@bugs.python.org> wrote:

Steven D'Aprano added the comment:

The behaviour is correct, this is not a bug. Each time you pop from aa, the following items move down one space. Then, the next time you pop, the items have moved:

['a0', 'b1', 'c2', 'd3', 'e4', 'f5', 'g6', 'h7', 'i8', 'j9', 'k10', 'l11']
d3 is the third item and gets popped;

['a0', 'b1', 'c2', 'e4', 'f5', 'g6', 'h7', 'i8', 'j9', 'k10', 'l11']
g6 is the fifth item and gets popped;

['a0', 'b1', 'c2', 'e4', 'f5', 'h7', 'i8', 'j9', 'k10', 'l11']
j9 is the seventh item and gets popped.

To get the result you want, you can use slicing:

aa[3:9:2]
=> returns ['d3', 'f5', 'h7']

then

del aa[3:9:2]
=> leaves ['a0', 'b1', 'c2', 'e4', 'g6', 'i8', 'j9', 'k10', 'l11']

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nosy: +steven.daprano
resolution:  -> not a bug
stage:  -> resolved
status: open -> closed

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Python tracker <report@bugs.python.org>
<http://bugs.python.org/issue24392>
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