Output of Python program | Set 6 (Lists)

Prerequisite – Lists in Python
Predict the output of the following Python programs. These question set will make you conversant with List Concepts in Python programming language.

  • Program 1
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    list1 = ['physics', 'chemistry', 1997, 2000]
      
    list2 = [1, 2, 3, 4, 5, 6, 7 ]
       
    print "list1[0]: ", list1[0]        #statement 1
    print "list1[0]: ", list1[-2]       #statement 2
    print "list1[-2]: ", list1[1:]      #statement 3
    print "list2[1:5]: ", list2[1:5]    #statement 4

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    Output:

    list1[0]:  physics
    list1[0]:  1997
    list1[-2]:  ['chemistry', 1997, 2000]
    list2[1:5]:  [2, 3, 4, 5]
    

    Explanation:
    To access values in lists, we use the square brackets for slicing along with the index or indices to obtain required value available at that index.For N items in a List MAX value of index will be N-1.
    Statement 1 : This will print item located at index 0 in Output.
    Statement 2 : This will print item located at index -2 i.e.second last element in Output.
    Statement 3 : This will print items located from index 1 to end of the list.
    Statement 4 : This will print items located from index 1 to 4 of the list.

  • Program 2
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    list1 = ['physics', 'chemistry', 1997, 2000]
      
    print "list1[1][1]: ", list1[1][1] #statement 1
      
    print "list1[1][-1]: ", list1[1][-1] #statement 2

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    Output:



    list1[1][1]:  h
    list1[1][-1]:  y
    

    Explanation:
    In python we can slice a list but we can also slice a element within list if it is a string. The declaration list[x][y] will mean that ‘x’ is the index of element within a list and ‘y’ is the index of entity within that string.

  • Program 3
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    list1 = [1998, 2002, 1997, 2000]
    list2 = [2014, 2016, 1996, 2009]
      
    print "list1 + list 2 = : ", list1 + list2   #statement 1
      
    print "list1 * 2 = : ", list1 * 2  #statement 2

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    Output:

    list1 + list 2 = :  [1998, 2002, 1997, 2000, 2014, 2016, 1996, 2009]
    list1 * 2 = :  [1998, 2002, 1997, 2000, 1998, 2002, 1997, 2000]
    
    

    Explanation:
    When addition(+) operator uses list as its operands then the two lists will get concatenated. And when a list id multiplied with a constant k>=0 then the same list is appended k times in the original list.

  • Program 4
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    list1 = range(100, 110) #statement 1
    print "index of element 105 is : ", list1.index(105#statement 2

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    Output:

    index of element 105 is :  5
    

    Explanation:
    Statement 1 : will genetrate numbers from 100 to 110 and appent all these numbers in the list.
    Statement 2 : will give the index value of 105 in the list list1.

  • Program 5
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    list1 = [1, 2, 3, 4, 5]
    list2 = list1
      
    list2[0] = 0;
      
    print "list1= : ", list1 #statement 2

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    Output:

    list1= :  [0, 2, 3, 4, 5]
    

    Explanation:
    In this problem, we have provided a reference to the list1 with another name list2 but these two lists are same which have two references(list1 and list2). So any alteration with list2 will affect the original list.

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