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for line in input_file:
	if '<treeitem' in line:     
		tree_level += 1
	elif '</treeitem>' in line:
 		tree_level -= 1
	else:
		pass

	if tree_level > 0:
		sub_menu_list.append(line)
	elif tree_level == 0 and len(sub_menu_list) > 0:
		print(sub_menu_list) # at this point sub_menu_list is filled with the correct data!
		menu_list.append(sub_menu_list)
		test_counter += 1
		print(test_counter) # number of loops fit to the menu structure --> correct
		print(sub_menu_list) # this is always correct, even at the first run
		print(menu_list) # first strange behavior: the very first element is empty. The first sub_menu_list hasn't been appended but all the others
		while len(sub_menu_list) > 0:
			del sub_menu_list[0]
		print(menu_list)  # at this point menu_list is filled with 17 * []. The number of [] is correct as we have 17 main menus. But why are they empty as I only append filled lists to this list???
	else:
		pass	

Code: Alles auswählen

In [287]: xs = []                                                               

In [288]: ys = []                                                               

In [289]: id(xs), id(ys)                                                        
Out[289]: (140709312221832, 140709312227400)

In [290]: xs.append(ys)                                                         

In [291]: xs.append(ys)                                                         

In [292]: xs                                                                    
Out[292]: [[], []]

In [293]: id(xs[0]), id(xs[1])                                                  
Out[293]: (140709312227400, 140709312227400)

In [294]: ys.append(42)                                                         

In [295]: ys                                                                    
Out[295]: [42]

In [296]: xs                                                                    
Out[296]: [[42], [42]]

In [297]: ys.clear()                                                            

In [298]: ys                                                                    
Out[298]: []

In [299]: xs                                                                    
Out[299]: [[], []]

Code: Alles auswählen

def f(x):
    x = 23

def g(items):
    items = [1, 2, 3]

def main():
    a = 42
    f(a)
    print(a)  # 23
    elements = [4, 7, 1, 1]
    g(elements)
    print(elements)  # [1, 2, 3]

Code: Alles auswählen

def g(items):
    items = [1, 2, 3]