["python","list","iteration"]
Adding element to list while iterating

I know that it is not allowed to remove elements while iterating a list, but is it allowed to add elements to a python list while iterating. Here is an example: for a in myarr: if somecond(a): myarr.append(newObj()) I have tried this in my code and it seems to work fine, however I don't know if it's because I am just lucky and that it will break at some point in the future? I prefer not to copy the list since myarr is huge, and therefore it would be too slow. Also I need to check the appended objects with somecond(). At some point somecond(a) will be false, so there can not be an infinite loop. Each object in myarr has a size, and each time somecond(a) is true and a new object is appended to the list, the new object will have a size smaller than a. somecond() has an epsilon for how small objects can be and if they are too small it will return "false".
You could use the islice from itertools to create an iterator over a smaller portion of the list. Then you can append entries to the list without impacting the items you're iterating over: islice(myarr, 0, len(myarr)-1) Even better, you don't even have to iterate over all the elements. You can increment a step size.