[Tutor] Why is this only catching one occurance?

[Bob Gailer]

Chris Hengge wrote:
> Here is my code:
> for unWantedItem in directoryList:
>             try:
>                 if "hex" in unWantedItem.lower():
>                     if not "bmc" in unWantedItem.lower():
>                        print unWantedItem + " removed!"
>                        directoryList.remove(unWantedItem)
>
> This only seems to loop through once, and removes 1 of 2 occurances 
> from this list that should be captured. Should "for" keep the list 
> going through each instance?
"for" goes thru the list accessing item[0], item[1], item[2], etc. Let's 
say "for" is on item[1] and you remove item[1]. All the subsequent items 
"move left", so item[2] becomes item[1], item[3] becomes item[2], etc. 
"for" then steps to item[2], skipping the original item[2].

There are several ways around this. The easiest is to process the list 
backwards: for unWantedItem in directoryList[,,-1]:

-- 
Bob Gailer
510-978-4454