How to empty a list

Question

It seems so  dirty  emptying a list in this way   while len alist   gt  0   alist pop     Does a clear way exist to do that

User · Answer

lst    0   has the same effect as  lst           It s a little simpler and maybe easier to remember  Other than that there s not much to say  The efficiency seems to be about the same

User · Answer

it turns out that with python 2 5 2  del l    is slightly slower than l         by 1 1 usec     python -mtimeit  l list range 1000     b l    del b     10000 loops  best of 3  29 8 usec per loop   python -mtimeit  l list range 1000     b l    b          10000 loops  best of 3  28 7 usec per loop   python -V Python 2 5 2

User · Answer

list        will reset list to an empty list   Note that you generally should not shadow reserved function names  such as list  which is the constructor for a list object -- you could use lst or list  instead  for instance

User · Answer

This actually removes the contents from the list  but doesn t replace the old label with a new empty list   del lst      Here s an example   lst1    1  2  3  lst2   lst1 del lst1    print lst2    For the sake of completeness  the slice assignment has the same effect   lst           It can also be used to shrink a part of the list while replacing a part at the same time  but that is out of the scope of the question    Note that doing lst      does not empty the list  just creates a new object and binds it to the variable lst  but the old list will still have the same elements  and effect will be apparent if it had other variable bindings

User · Answer

If you re running Python 3 3 or better  you can use the clear   method of list  which is parallel to clear   of dict  set  deque and other mutable container types   alist clear      removes all items from alist  equivalent to del alist       As per the linked documentation page  the same can also be achieved with alist    0   To sum up  there are four equivalent ways to clear a list in-place  quite contrary to the Zen of Python      alist clear      Python 3 3  del alist    alist         alist    0

User · Answer

Another simple code you could use  depending on your situation  is   index len list -1  while index gt  0      del list index      index- 1   You have to start index at the length of the list and go backwards versus index at 0  forwards because that would end you up with index equal to the length of the list with it only being cut in half   Also  be sure that the while line has a  greater than or equal to  sign  Omitting it will leave you with list 0  remaining

User · Answer

You could try   alist           Which means  Splice in the list     0 elements  at the location      all indexes from start to finish   The     is the slice operator  See this question for more information

[python] How to empty a list?

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