Prerequisite - Lists in Python 
Predict the output of the following Python programs.
 

• Program 1 
   

list = [1, 2, 3, None, (1, 2, 3, 4, 5), ['Geeks', 'for', 'Geeks']]
print len(list)

list = [1, 2, 3, None, (1, 2, 3, 4, 5), ['Geeks', 'for', 'Geeks']]

print len(list)

• 
  Output: 
   

6

• 
  Explanation: 
  The beauty of python list datatype is that within a list, a programmer can nest another list, a dictionary or a tuple. Since in the code there are 6 items present in the list the length of the list is 6.
   
• Program 2 
   

list = ['python', 'learning', '@', 'Geeks', 'for', 'Geeks']

print list[::]          
print list[0:6:2]       
print list[ :6: ]       
print list[ :6:2]      
print list[ ::3]       
print list[ ::-2]     

list = ['python', 'learning', '@', 'Geeks', 'for', 'Geeks']

​

print list[::]          

print list[0:6:2]       

print list[ :6: ]       

print list[ :6:2]      

print list[ ::3]       

print list[ ::-2]

• 
  Output: 
   

['python', 'learning', '@', 'Geeks', 'for', 'Geeks']
['python', '@', 'for']
['python', 'learning', '@', 'Geeks', 'for', 'Geeks']
['python', '@', 'for']
['python', 'Geeks']
['Geeks', 'Geeks', 'learning']

• 
  Explanation: 
  In python list slicing can also be done by using the syntax listName[x:y:z] where x means the initial index, y-1 defines the final index value and z specifies the step size. If anyone of the values among x, y and z is missing the interpreter takes default value.
  Note: 
  1. For x default value is 0 i.e. start of the list. 
  2. For y default value is length of the list. 
  3. For z default value is 1 i.e. every element of the list.
   
• Program 3 
   

d1 = [10, 20, 30, 40, 50]
d2 = [1, 2, 3, 4, 5]
print d1 - d1

d1 = [10, 20, 30, 40, 50]

d2 = [1, 2, 3, 4, 5]

print d1 - d1

• 
  Output: 
   

No Output

• 
  Explanation: 
  Unlike addition or relational operators not all the arithmetic operators can use lists as their operands. Since - minus operator can't take lists as its operand no output will be produced. Program will produce following error. 
   

TypeError: unsupported operand type(s) for -: 'list' and 'list'

• 
   
• Program 4

list = ['a', 'b', 'c', 'd', 'e']
print list[10:]

list = ['a', 'b', 'c', 'd', 'e']

print list[10:]

• 
  Output: 
   

[]

• 
  Explanation: 
  As one would expect, attempting to access a member of a list using an index that exceeds the number of members (e.g., attempting to access list[10] in the list above) results in an IndexError. However, attempting to access a slice of a list at a starting index that exceeds the number of members in the list will not result in an IndexError and will simply return an empty list. 
   
• Program 5 
   

list = ['a', 'b', 'c']*-3
print list

list = ['a', 'b', 'c']*-3

print list

• 
  Output: 
   

[]

• 
  Explanation: 
  A expression list[listelements]*N where N is a integer appends N copies of list elements in the original list. If N is a negative integer or 0 output will be a empty list else if N is positive list elements will be added N times to the original list.