How to remove an element from a list by index

Question

How do I remove an element from a list by index in Python   I found the list remove method  but say I want to remove the last element  how do I do this  It seems like the default remove searches the list  but I don t want any search to be performed

User · Answer

It has already been mentioned how to remove a single element from a list and which advantages the different methods have. Note, however, that removing multiple elements has some potential for errors:

>>> l = [0,1,2,3,4,5,6,7,8,9]
>>> indices=[3,7]
>>> for i in indices:
...     del l[i]
... 
>>> l
[0, 1, 2, 4, 5, 6, 7, 9]

Elements 3 and 8 (not 3 and 7) of the original list have been removed (as the list was shortened during the loop), which might not have been the intention. If you want to safely remove multiple indices you should instead delete the elements with highest index first, e.g. like this:

>>> l = [0,1,2,3,4,5,6,7,8,9]
>>> indices=[3,7]
>>> for i in sorted(indices, reverse=True):
...     del l[i]
... 
>>> l
[0, 1, 2, 4, 5, 6, 8, 9]

User · Answer

You can use either del or pop to remove element from list based on index   Pop will print member it is removing from list  while list delete that member without printing it    gt  gt  gt  a  1 2 3 4 5   gt  gt  gt  del a 1   gt  gt  gt  a  1  3  4  5   gt  gt  gt  a pop 1   3  gt  gt  gt  a  1  4  5   gt  gt  gt

User · Answer

It doesn t sound like you re working with a list of lists  so I ll keep this short   You want to use pop since it will remove elements not elements that are lists  you should use del for that   To call the last element in python it s  -1    gt  gt  gt  test     item1    item2    gt  gt  gt  test pop -1   item2   gt  gt  gt  test   item1

User · Answer

As previously mentioned  best practice is del    or pop   if you need to know the value   An alternate solution is to re-stack only those elements you want       a     a    b    c    d         def remove element list  index            clipboard              for i in range len list                 if i is not index                   clipboard append list  i           return clipboard      print remove element a 2         gt  gt    a    b    d     eta  hmm    will not work on negative index values  will ponder and update  I suppose   if index  lt 0 index  len list   index    would patch it    but suddenly this idea seems very brittle  Interesting thought experiment though   Seems there should be a  proper  way to do this with append     list comprehension     pondering

User · Answer

l - list of values  we have to remove indexes from inds2rem list   l   range 20  inds2rem    2 5 1 7  map lambda x  l pop x   sorted inds2rem  key   lambda x -x     gt  gt  gt  l  0  3  4  6  8  9  10  11  12  13  14  15  16  17  18  19

User · Answer

Or if multiple indexes should be removed   print  v for i v in enumerate your list  if i not in list of unwanted indexes     Of course then could also do   print  v for i v in enumerate your list  if i    unwanted index

User · Answer

If you want to remove the specific position element in a list  like the 2th  3th and 7th  you can t use  del my list 2  del my list 3  del my list 7    Since after you delete the second element  the third element you delete actually is the fourth element in the original list  You can filter the 2th  3th and 7th element in the original list and get a new list  like below   new list    j for i  j in enumerate my list  if i not in  2  3  7

User · Answer

One can either use del or pop  but I prefer del  since you can specify index and slices  giving the user more control over the data   For example  starting with the list shown  one can remove its last element with del as a slice  and then one can remove the last element from the result using pop    gt  gt  gt  l    1 2 3 4 5   gt  gt  gt  del l -1    gt  gt  gt  l  1  2  3  4   gt  gt  gt  l pop -1  4  gt  gt  gt  l  1  2  3

User · Answer

You probably want pop   a     a    b    c    d   a pop 1     now a is   a    c    d     By default  pop without any arguments removes the last item   a     a    b    c    d   a pop      now a is   a    b    c

User · Answer

Generally  I am using the following method    gt  gt  gt  myList    10 20 30 40 50   gt  gt  gt  rmovIndxNo   3  gt  gt  gt  del myList rmovIndxNo   gt  gt  gt  myList  10  20  30  50

User · Answer

Yet another way to remove an element s  from a list by index   a    0  1  2  3  4  5  6  7  8  9     remove the element at index 3 a 3 4         a is now  0  1  2  4  5  6  7  8  9     remove the elements from index 3 to index 6 a 3 7         a is now  0  1  2  7  8  9    a x y  points to the elements from index x to y-1  When we declare that portion of the list as an empty list       those elements are removed

User · Answer

Like others mentioned pop and del are the efficient ways to remove an item of given index  Yet just for the sake of completion  since the same thing can be done via many ways in Python    Using slices  this does not do in place removal of item from original list     Also this will be the least efficient method when working with Python list  but this could be useful  but not efficient  I reiterate  when working with user defined objects that do not support pop  yet do define a   getitem        gt  gt  gt  a    1  2  3  4  5  6   gt  gt  gt  index   3   Only positive index   gt  gt  gt  a   a  index    a index 1      a is now  1  2  3  5  6    Note  Please note that this method does not modify the list in place like pop and del  It instead makes two copies of lists  one from the start until the index but without it  a  index   and one after the index till the last element  a index 1     and creates a new list object by adding both  This is then reassigned to the list variable  a   The old list object is hence dereferenced and hence garbage collected  provided the original list object is not referenced by any variable other than a    This makes this method very inefficient and it can also produce undesirable side effects  especially when other variables point to the original list object which remains un-modified    Thanks to  MarkDickinson for pointing this out      This Stack Overflow answer explains the concept of slicing   Also note that this works only with positive indices   While using with objects  the   getitem   method must have been defined and more importantly the   add   method must have been defined to return an object containing items from both the operands   In essence  this works with any object whose class definition is like   class foo object       def   init   self  items           self items   items      def   getitem   self  index           return foo self items index        def   add   self  right           return foo  self items   right items     This works with list which defines   getitem   and   add   methods   Comparison of the three ways in terms of efficiency   Assume the following is predefined   a   range 10  index   3   The del object index  method   By far the most efficient method  It works will all objects that define a   del   method   The disassembly is as follows   Code   def del method        global a     global index     del a index    Disassembly    10    0 LOAD GLOBAL     0  a         3 LOAD GLOBAL     1  index         6 DELETE SUBSCR     This is the line that deletes the item        7 LOAD CONST      0  None        10 RETURN VALUE None   pop method   It is less efficient than the del method and is used when you need to get the deleted item   Code   def pop method        global a     global index     a pop index    Disassembly    17     0 LOAD GLOBAL     0  a          3 LOAD ATTR       1  pop          6 LOAD GLOBAL     2  index          9 CALL FUNCTION   1        12 POP TOP        13 LOAD CONST      0  None         16 RETURN VALUE   The slice and add method   The least efficient   Code   def slice method        global a     global index     a   a  index    a index 1     Disassembly    24     0 LOAD GLOBAL    0  a          3 LOAD GLOBAL    1  index          6 SLICE 2         7 LOAD GLOBAL    0  a         10 LOAD GLOBAL    1  index         13 LOAD CONST     1  1         16 BINARY ADD        17 SLICE 1        18 BINARY ADD        19 STORE GLOBAL   0  a         22 LOAD CONST     0  None         25 RETURN VALUE None   Note  In all three disassembles ignore the last two lines which basically are return None  Also the first two lines are loading the global values a and index

User · Answer

Use del and specify the index of the element you want to delete    gt  gt  gt  a    0  1  2  3  4  5  6  7  8  9   gt  gt  gt  del a -1   gt  gt  gt  a  0  1  2  3  4  5  6  7  8    Also supports slices    gt  gt  gt  del a 2 4   gt  gt  gt  a  0  1  4  5  6  7  8  9    Here is the section from the tutorial

User · Answer

You could just search for the item you want to delete  It is really simple  Example       letters     a    b    c    d    e       letters remove letters 1       print  letters    Used with a   to make it unpack you don t have to  Python 3 x or newer    Output  a c d e

User · Answer

pop is also useful to remove and keep an item from a list   Where del actually trashes the item    gt  gt  gt  x    1  2  3  4    gt  gt  gt  p   x pop 1   gt  gt  gt  p     2

User · Answer

Use the following code to remove element from the list    list    1  2  3  4  list remove 1  print list   output    2  3  4    If you want to remove index element data from the list use   list    1  2  3  4  list remove list 2   print list  output    1  2  4

User · Answer

This depends on what you want to do   If you want to return the element you removed  use pop      gt  gt  gt  l    1  2  3  4  5   gt  gt  gt  l pop 2  3  gt  gt  gt  l  1  2  4  5    However  if you just want to delete an element  use del    gt  gt  gt  l    1  2  3  4  5   gt  gt  gt  del l 2   gt  gt  gt  l  1  2  4  5    Additionally  del allows you to use slices  e g  del 2

User · Answer

Use the del statement  del listName -N   For example  if you want to remove the last 3 items  your code should be  del listName -3    For example  if you want to remove the last 8 items  your code should be  del listName -8

[python] How to remove an element from a list by index

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