Question

def group_move(group, damper):
    # Make a copy to test values
    new = group

    # See what the original group value is
    print("Test = " + str(group.ctris[0].p1.x))
    dr = some float
    dx = some float
    dy = some float
    # Make changes to new
    moveGroup(new, dr, dx, dy)
    # See if those changes produce allowed values
    if (off_board_check(new) == 1):
        damper += 2.0
        # Reset to original to try again
        print("Test Here = " + str(group.ctris[0].p1.x))
        group_move(group, damper)
    else:
        # If everything is on the board, then make the change
        group = new

If I run this, I will see that on the very first recursion, the Test print line produces a different value from the Test Here print line. Why? How is this code possibly affecting the values of group? I am trying to pass an unchanged group onto the next recursive level of group_move in the case that the test values failed, but it seems that group is somehow being affected before I even make any recursive calls. How is the above any different from this:

>>> x = 1
>>> y = x
>>> x = 7
>>> y = 77
>>> x
7
>>> y
77

Answer 1

# Make a copy to test values
new = group

The comment is incorrect. That does not make a copy. All that does is make a variable named new point at the same object that group is pointing at.

If you want to create an actual copy, you may want to look at copy.deepcopy().