Remove related element from list while iterating in python-CodePudding

I need to reduce the size of a list iteratively based on an equivalence condition. The idea is that I iterate in the list and, for each element, I eliminate all the elements of the list related (equivalent) to that element.

For example, consider that G is a list of tuples. I want to eliminate all tuples that can be obtained as a permutation of another tuple already in the list. Let equiv(g) be the function that returns a list of all permutations of g (excluding g itself).

I tried this code:

for g in G:
    for gg in equiv(g):
        if gg in GN:
            G.remove(gg)

This should leave in the list only one element for each equivalence class. However, it doesn't seem to work properly. I suspect I am doing it the wrong way.

Note that I cannot iterate over a copy of the list G, as suggested for example here, because in this way all elements of each class of equivalence would be removed. In other words, I don't want to remove based on elements what have already been removed.

CodePudding user response：

For loop iterate through the list by incrementing the indexes, which will have problems if you delete elements and refreshes the index. Try to use while loop pop

new_G = []
while len(G) > 0:
    g = G.pop(0)
    for gg in equiv(g):
        G.remove(gg)
    new_G.append(g)