Is there any reason to do anything more complicated than one of these two lines when you want to clear a list in Python?
old_list = []
old_list = list()
The reason I ask is that I just saw this in some running code:
del old_list[ 0:len(old_list) ]
Answer
Clearing a list in place will affect all other references of the same list.
For example, this method doesn't affect other references:
>>> a = [1, 2, 3]
>>> b = a
>>> a = []
>>> print(a)
[]
>>> print(b)
[1, 2, 3]
But this one does:
>>> a = [1, 2, 3]
>>> b = a
>>> del a[:] # equivalent to del a[0:len(a)]
>>> print(a)
[]
>>> print(b)
[]
>>> a is b
True
You could also do:
>>> a[:] = []