PPA-6

Question

Scores Dataset Revisited

Recall the Scores dataset from CT. We shall be using a variant of this dataset for this problem. Each student-entry in the dataset is represented as a dictionary. For example, one of the entries would look like this:

{'SeqNo': 1, 'Name': 'Devika', 
 'Gender': 'F', 'City': 'Bengaluru',
 'Mathematics': 85, 'Physics': 100, 'Chemistry': 79,
 'Biology': 75, 'Computer Science': 88, 
 'History': 60, 'Civics': 88, 'Philosophy': 95}

All keys of the dict are strings. For SeqNo and all the subjects, the corresponding values are integers. The values corresponding to Name, Gender and City are strings.

The entire dataset is represented as a list of dictionaries. That is, each element of the list will be a dictionary like the one given above. This list is named scores_dataset. The SeqNo is a unique identifier for each student that runs from \(0\) to \(n - 1\), where \(n\) is the total number of students in the dataset.

Write a function named get_marks that accepts the scores_dataset and a variable named subject as arguments. It should return the marks scored by all students in subject as a list of tuples. Each element in this list is of the form (Name, Marks). The order in which the tuples are appended to the list doesn’t matter

  • You do not have to accept input from the user or print the output to the console. You just have to write the definition of the function.
  • Do not try to process the output produced. We randomly sample five elements from the list returned by your function and print that in the desired form.

Solution

Let us consider the dictionary for one student:

student = {
    'SeqNo': 1, 
    'Name': 'Devika', 
    'Gender': 'F', 
    'City': 'Bengaluru', 
    'Mathematics': 85, 
    'Physics': 100, 
    'Chemistry': 79, 
    'Biology': 75, 
    'Computer Science': 88, 
    'History': 60, 
    'Civics': 88, 
    'Philosophy': 95
}

What we need is a tuple of the form (name, marks). If the subject is Physics, then this tuple is:

(student['Name'], student['Physics'])

All that we need to do is iterate over each student in the scores_dataset. Note that the dataset is a list of dictionaries. One such dictionary is student as shown above.

def get_marks(scores_dataset, subject):
    marks = [ ]
    for student in scores_dataset:
        T = (student['Name'], student[subject])
        marks.append(T)
    return marks

This is the same as the previous method. Rather than creating an intermediate variable, the tuple is directly appended to marks.

def get_marks(scores_dataset, subject):
    marks = [ ]
    for student in scores_dataset:
        marks.append((student['Name'], 
                      student[subject]))
    return marks

Note the loop variable that we have used: student. This is an apt choice because each element in scores_dataset is a dictionary that corresponds to some student. Good choice of loop variables greatly improves the readability of code.

Note

  • Avoid indiscriminate use of i and j as loop variables. Reserve them for specific uses like iterating through matrices.

  • Avoid for i in range(len(L)) construct and instead use for item in L wherever possible.