Working With Lists In Python Programing

 

append() :Appending elements to a list 

Adds a single item to the end of the list. Does not return a new list, just modifies the original.

L=[12,13,14,15]  L.append(16)  print(L) Out[1]: [12, 13, 14, 15, 16]  L2=[21,22]  L.append([21,22])  print(L) Out[2]: [12, 13, 14, 15, 16, [21, 22]]  print(L2) Out[3]: [21, 22]  L3=L.append(32)  print(L3) Out[4]: [12, 13, 14, 15, 16, [21, 22], 32]

extend() :Appending multiple elements to a list 

append() adds one element to a list, extend() can add multiple elements from a list supplied to it as an argument. Returns no value. 

L3=L.append(34,37)  TypeError: append() takes exactly one argument (2 given)  print(L) Out[1]: [12, 13, 14, 15, 16, [21, 22], 32]  L.extend([43,46])  print(L) Out[2]: [12, 13, 14, 15, 16, [21, 22], 32, 43, 46]  L.extend(23,24)  TypeError: extend() takes exactly one argument (2 given)

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[2]: [11, 12, 13, 14, 15, 19]  L.insert(9,19)  print(L) Out[3]: [11, 12, 13, 14, 15, 19, 19]  L.insert(-9,19)  print(L) Out[4]: [19, 11, 12, 13, 14, 15, 19, 19]  L.insert(3,19)  print(L) Out[5]: [19, 11, 12, 19, 13, 14, 15, 19, 19]

Updating elements to a list 

To update or change and element of the list in place, you just have to assign new values to the element’s index in list as per Syntax :

L[index] = <new value>

L=[11,12,13,14,15]  L[0]=21  print(L) Out[1]: [21, 12, 13, 14, 15]  L[5]=21 IndexError: list assignment index out of range

Deleting Elements from a List 

The del statement can be used to remove an individual item, or to remove all the items identified by a slice . It is to be lost as per Syntax given below: 

del List[<index>]

del List[<start>:<stop>] 

print(L) Out[1]: [21, 12, 13, 14, 15]  del L[1]  print(L) Out[2]: [21, 13, 14, 15]  del L[1:3]  print(L) Out[3]: [21, 15]

List.sort()  

• Sorts the items of the list in place.  

• The default order is increasing.  

• To reverse in decreasing order, reverse=True is used.  

• Returns nothing. 

L=[13,2,456,1,11,432,32]  L.sort()  print(L) Out[1]: [1, 2, 11, 13, 32, 432, 456]  L=[13,2,456,1,11,432,32]  L.sort(reverse=True)  print(L) Out[2]: [456, 432, 32, 13, 11, 2, 1]

If the elements within a list consist of complex numbers, sort() will not work.