Published and synced page for Students

Activity 3: Python - JSON handling

Intro

Extending file handling concepts from Activity 2, this activity introduces manipulation of JSON files. We also introduce the concept of Python Classes. Classes encapsulate data (attributes) and behavior (methods), inheritance into a single unit, making it easier to organize and manage code

Prerequisites

• https://docs.python.org/3/tutorial/classes.html
• https://www.w3schools.com/python/python_classes.asp
• https://www.w3schools.com/python/python_dictionaries.asp (JSON files are loaded as python dictionaries. Some elements of a JSON dictionary are itself dictionaries ie dictionary inside dictionary)
• https://en.wikipedia.org/wiki/JSON
• https://docs.python.org/3/library/json.html
• https://realpython.com/python-type-checking/

Tasks

<aside> 💡 Each method defined in the template is a member of a class called PQM_Metrics. To call this method use the following syntax

</aside>

# This is just sample code and do not represent actual class or memeber variable 
#names for the Activity.
class_var = TestClass() #This is a class instantiation
class_var.variable_1 = 1 #Accessing class variables and updating it
class_var.method_1() #Calling a method defined in the class

The JSON should be read, sanitized and stored using the following logic

pqm_metric_instance = PQM_Metrics() #Instantiate the class variable
pqm_metric_instance.store_and_sanitize_json('file.json') # You need to define the logic
print(pqm_metric_instance.src_json_dict) #Prints sanitized JSON of type <class 'dict'>

<aside> 💡 The above method is provided in the template. Populate it with the correct logic. This method will be used in the auto-grading as well

</aside>

This task is a pre-requisite for 4 and 5 | When a JSON file path is sent to the method, it is cleaned and stored in the class variable

NOTE: Method does not return anything | 40 | | 2.1 The JSON contains an outer dictionary of elements. Use the get_json_keys method to return a python list of keys of the outermost dictionary | The method should return the list of the outermost elements of the JSON | 10 | | 3.1 The JSON contains an element called metrics which is another dictionary. Return the total number of cells present in this dictionary using the method get_cell_count | Return the total number of cells in the metrics element as an integer | 10 | | 4.1 Compute the average completeness, artifacts, resolution and accuracy of all the cells in the metrics element using get_avg_metrics method 4.2 This method should update the respective class variables.

This method does not return anything | The average values of 4 metrics is stored in the class variables.

Note that since the metrics lie in the range of [0,1], the average must not exceed 1 or lie below 0

NOTE: Method does not return anything | 20 | | 5.1 Populate the compute_sums method to compute the sum of the chamfer, hausdorff and normalized chamfer values of all cells of the metrics element and store it in the respective class variables | Total sum of each of the defined metric is stored in the class variables

Note that this value can be greater than 1.

NOTE: Method does not return anything | 20 |

JSON Notation

Reference for JSON level notation

{
    "level_1_1":{
        "level_2_1":0,
        "level_2_2":{
            "level_3_1":0,
            "level_3_2":0,
        }
    },
    "level_1_2":0,
}