List Functions And Methods In Python Programing

List.pop(<index>)

• Deletes an element from the given position in the list, and returns it.

• If no index, pop() removes and returns the last item in the list.

• Returns the item being deleted 

• Raises an exception (runtime error) if the list is already empty 

L=[21,12,13,14,15]  print(L.pop()) Out[1]: 15  print(L.pop(2)) Out[1]: 13  print(L) Out[1]: [21, 12, 14]  print(L.pop(5) IndexError: pop index out of range

List.index(<item>)  

• Returns the index of first matched item from the list  

• If the given item is not in the list, it raises an exception error. 

L=[11,12,13,14,15]  print(L.index(13) )  Out[1]: 2  print(L.index(20) ) ValueError: 20 is not in list

List.insert(<pos>,<item>)

• Append() and extend() insert the element(s) at the end of the list 

• If you want to insert an element somewhere in between or any position of your choice, insert() method is used. 

• <pos> is the index of the element before which the second argument is to be added 

• Returns no value 

print(L) Out[1]: [11, 12, 13, 14, 15]  L.insert(5,19)  print(L) Out[1]: [11, 12, 13, 14, 15, 19]  L.insert(9,19)  print(L) Out[1]: [11, 12, 13, 14, 15, 19, 19]  L.insert(-9,19)  print(L) Out[1]: [19, 11, 12, 13, 14, 15, 19, 19]  L.insert(3,19)  Out[1]: [19, 11, 12, 19, 13, 14, 15, 19, 19]

List.remove(<value>) 

• remove() function removes the first occurrence of given item from the list.

• Does not return anything.  

• pop() removes an element from the list based on index, but to remove an element based on value, remove() is used. 

print(L)  Out[1]: [19, 11, 12, 19, 13, 14, 15, 19, 19]  L.remove(11) print(L) Out[1]: [19, 12, 19, 13, 14, 15, 19, 19]  L.remove(19) print(L) Out[1]: [12, 19, 13, 14, 15, 19, 19]  L.remove(1) ValueError: list.remove(x): x not in list

List.clear()  

• Removes all items from the list .  

• The list becomes empty after clear() is executed.  

• Returns nothing. 

How is del L different from L.clear()?  

• del L removes the elements as well as the list.  

• L.clear() only removes the elements from the List. The List remains. The List object still exists as an empty list. 

L=[1,2,3,4]  del L print(L) NameError: name 'L' is not defined  L=[1,2,3,4]  L.clear()  print(L) Out[1]: [ ]

List.count(<item>)  

• Returns the count of the item passed as an argument.  

• If the element is not in the list, it returns 0. 

L=[11,12,13,19,14,19,16,19,19]  print(L.count(19) ) Out[1]: 4  print(L.count(9) ) Out[1]: 0

List.reverse()  

• Reverses the item of the list in place.  

• No new list is created.  

• Returns no list. 

L=[11,12,13,14,15]  L.reverse()  print(L) Out[1]: [15, 14, 13, 12, 11]  L2=L.reverse()  print(L2) Out[1]: [15, 14, 13, 12, 11]