Difference between del remove and pop on lists

Question

gt  gt  gt  a  1 2 3   gt  gt  gt  a remove 2   gt  gt  gt  a  1  3   gt  gt  gt  a  1 2 3   gt  gt  gt  del a 1   gt  gt  gt  a  1  3   gt  gt  gt  a   1 2 3   gt  gt  gt  a pop 1  2  gt  gt  gt  a  1  3   gt  gt  gt     Is there any difference between the above three methods to remove an element from a list

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pop  Takes index  when given  else take last   removes value at that index  and returns value  remove  Takes value  removes first occurrence  and returns nothing  delete  Takes index  removes value at that index  and returns nothing

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You can also use remove to remove a value by index as well     n    1  3  5   n remove n 1     n would then refer to  1  5

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Since no-one else has mentioned it  note that del  unlike pop  allows the removal of a range of indexes because of list slicing    gt  gt  gt  lst    3  2  2  1   gt  gt  gt  del lst 1    gt  gt  gt  lst  3    This also allows avoidance of an IndexError if the index is not in the list    gt  gt  gt  lst    3  2  2  1   gt  gt  gt  del lst 10    gt  gt  gt  lst  3  2  2  1

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Use del to remove an element by index  pop   to remove it by index if you need the returned value  and remove   to delete an element by value   The last requires searching the list  and raises ValueError if no such value occurs in the list  When deleting index i from a list of n elements  the computational complexities of these methods are del     O n - i  pop     O n - i  remove  O n

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The remove operation on a list is given a value to remove  It searches the list to find an item with that value and deletes the first matching item it finds  It is an error if there is no matching item  raises a ValueError    gt  gt  gt  x    1  0  0  0  3  4  5   gt  gt  gt  x remove 4   gt  gt  gt  x  1  0  0  0  3  5   gt  gt  gt  del x 7  Traceback  most recent call last     File   lt pyshell 1 gt    line 1  in  lt module gt      del x 7  IndexError  list assignment index out of range   The del statement can be used to delete an entire list  If you have a specific list item as your argument to del  e g  listname 7  to specifically reference the 8th item in the list   it ll just delete that item  It is even possible to delete a  slice  from a list  It is an error if there index out of range  raises a IndexError    gt  gt  gt  x    1  2  3  4   gt  gt  gt  del x 3   gt  gt  gt  x  1  2  3   gt  gt  gt  del x 4  Traceback  most recent call last     File   lt pyshell 1 gt    line 1  in  lt module gt      del x 4  IndexError  list assignment index out of range   The usual use of pop is to delete the last item from a list as you use the list as a stack  Unlike del  pop returns the value that it popped off the list  You can optionally give an index value to pop and pop from other than the end of the list  e g listname pop 0  will delete the first item from the list and return that first item as its result   You can use this to make the list behave like a queue  but there are library routines available that can provide queue operations with better performance than pop 0  does  It is an error if there index out of range  raises a IndexError    gt  gt  gt  x    1  2  3    gt  gt  gt  x pop 2   3   gt  gt  gt  x   1  2   gt  gt  gt  x pop 4  Traceback  most recent call last     File   lt pyshell 1 gt    line 1  in  lt module gt      x pop 4  IndexError  pop index out of range   See collections deque for more details

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Already answered quite well by others  This one from my end     Evidently  pop is the only one which returns the value  and remove is the only one which searches the object  while del limits itself to a simple deletion

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Many best explanations are here but I will try my best to simplify more  Among all these methods  remove  amp  pop are postfix while delete is prefix  remove    It used to remove first occurrence of element remove i    gt  first occurrence of i value  gt  gt  gt  a    0  2  3  2  1  4  6  5  7   gt  gt  gt  a remove 2      where i   2  gt  gt  gt  a  0  3  2  1  4  6  5  7   pop    It used to remove element if  unspecified pop     gt  from end of list  gt  gt  gt a pop    gt  gt  gt a  0  3  2  1  4  6  5   specified pop index    gt  of index  gt  gt  gt a pop 2   gt  gt  gt a  0  3  1  4  6  5   WARNING  Dangerous Method Ahead delete    Its a prefix method  Keep an eye on two different syntax for same method     and     It possesses power to  1 Delete index del a index    gt  used to delete index and its associated value just like pop   gt  gt  gt del a 1   gt  gt  gt a  0  1  4  6  5   2 Delete values in range  index 1 index N  del a 0 3    gt  multiple values in range  gt  gt  gt del a 0 3   gt  gt  gt a  6  5   3 Last but not list  to delete whole list in one shot del  a    gt  as said above   gt  gt  gt del  a   gt  gt  gt a  Hope this clarifies the confusion if any

User · Answer

Remove basically works on the value   Delete and pop work on the index  Remove basically removes the first matching value  Delete deletes the item from a specific index Pop basically takes an index and returns the value at that index  Next time you print the list the value doesnt appear

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Any operation function on different data structures is defined for particular actions  Here in your case i e  removing an element  delete  Pop and remove   If you consider sets  Add another operation - discard  Other confusing case is while adding  Insert Append   For Demonstration  Let us Implement deque  deque is a hybrid linear data structure  where you can add elements   remove elements from both ends  Rear and front Ends    class Deque object      def   init   self        self items       def addFront self item        return self items insert 0 item    def addRear self item        return self items append item    def deleteFront self        return self items pop 0    def deleteRear self       return self items pop     def returnAll self        return self items      In here  see the operations   def deleteFront self        return self items pop 0  def deleteRear self       return self items pop     Operations have to return something  So  pop -  With and without an index   If I don t want to return the value  del self items 0   Delete by value not Index     remove     list ez  1 2 3 4 5 6 7 8  for i in list ez      if i 2  0          list ez remove i  print list ez    Returns  1 3 5 7   let us consider the case of sets   set ez set ez set range 10    set ez remove 11     Gives Key Value Error     KeyError  11  set ez discard 11     Does Not return any errors

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While pop and delete both take indices to remove an element as stated in above comments  A key difference is the time complexity for them  The time complexity for pop   with no index is O 1  but is not the same case for deletion of last element   If your use case is always to delete the last element  it s always preferable to use pop   over delete    For more explanation on time complexities  you can refer to https   www ics uci edu  pattis ICS-33 lectures complexitypython txt

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Here is a detailed answer  del can be used for any class object whereas pop and remove and bounded to specific classes  For del Here are some examples  gt  gt  gt  a   5  gt  gt  gt  b    quot this is string quot   gt  gt  gt  c   1 432  gt  gt  gt  d   myClass     gt  gt  gt  del c  gt  gt  gt  del a  b  d     we can use comma separated objects  We can override   del   method in user-created classes  Specific uses with list  gt  gt  gt  a    1  4  2  4  12  3  0   gt  gt  gt  del a 4   gt  gt  gt  a  1  4  2  4  3  0    gt  gt  gt  del a 1  3      we can also use slicing for deleting range of indices  gt  gt  gt  a  1  4  3  0   For pop pop takes the index as a parameter and removes the element at that index Unlike del  pop when called on list object returns the value at that index  gt  gt  gt  a    1  5  3  4  7  8   gt  gt  gt  a pop 3     Will return the value at index 3 4  gt  gt  gt  a  1  5  3  7  8   For remove remove takes the parameter value and remove that value from the list  If multiple values are present will remove the first occurrence Note  Will throw ValueError if that value is not present  gt  gt  gt  a    1  5  3  4  2  7  5   gt  gt  gt  a remove 5     removes first occurence of 5  gt  gt  gt  a  1  3  4  2  7  5   gt  gt  gt  a remove 5   gt  gt  gt  a  1  3  4  2  7   Hope this answer is helpful

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The effects of the three different methods to remove an element from a list  remove removes the first matching value  not a specific index   gt  gt  gt  a    0  2  3  2   gt  gt  gt  a remove 2   gt  gt  gt  a  0  3  2   del removes the item at a specific index   gt  gt  gt  a    9  8  7  6   gt  gt  gt  del a 1   gt  gt  gt  a  9  7  6   and pop removes the item at a specific index and returns it   gt  gt  gt  a    4  3  5   gt  gt  gt  a pop 1  3  gt  gt  gt  a  4  5   Their error modes are different too   gt  gt  gt  a    4  5  6   gt  gt  gt  a remove 7  Traceback  most recent call last     File  quot  lt stdin gt  quot   line 1  in  lt module gt  ValueError  list remove x   x not in list  gt  gt  gt  del a 7  Traceback  most recent call last     File  quot  lt stdin gt  quot   line 1  in  lt module gt  IndexError  list assignment index out of range  gt  gt  gt  a pop 7  Traceback  most recent call last     File  quot  lt stdin gt  quot   line 1  in  lt module gt  IndexError  pop index out of range

[python] Difference between del, remove, and pop on lists

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