Output of Python programs | Set 8

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

• Program 1
  

Python

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
  

Python

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
  

Python

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

Python

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
  

Python

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. 
  

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