performance degradation when looping through lists

[diffuser78 at gmail.com]

Hi,

I wrote a program some days back and I was using lists heavily for
performing operations such as pop, remove, append. My list size was
around 1024x3 and there were around 20 different objects like this.

What I want to ask you is that my program also degraded over a period
of time. I cannot post the code as its lot of code.

 But I want to ask a question why List degrade. What other alternative
for lists is a faster measure. 

Eveyr help is greatly appreciated,