Records

Course Content

Create a user defined record
Use these records to store collections of data
Perform standard algorithms on arrays of records

For our BMI program we were storing 3 values in 3 parallel arrays:

Height
Weight
BMI

We can store these in one record structure where each one will have these 3 pieces of data (or fields).

Defining a record in Pseudocode

RECORD BMI:

Height : REAL

Weight: REAL

BMI: REAL

END RECORD

This defines a data structure that has 3 pieces of information. It is important to indicate the type of each field.

But we will need to have an array of these as we will be holding details about numerous people so...

Using a single record in Pseudocode

If we need to declare a single BMI variable

DECLARE BMIrecord AS BMI

And then to use the different ‘fields’ we can use the following:

BMIrecord.height = 1.6

BMIrecord.weight = 62.3

BMIrecord.BMI = BMIrecord.weight * (BMIrecord.height ^ 2)

A Single record in Python

Declares a dataclass called BMI ( not officially a record but is what we will use in Python. This is only available in Python 3.7 and above.

Declares a single BMI Record.

And then assigns the values in the relevant fields and then calculates the BMI.

Displays the height, weight and BMI fields of the record we just calculated.

Using arrays of records in Python

As we want to store numerous records such as in the table shown:

We will need to declare an array of records to store each of the set of fields. So there would need to be an array of 4 records.

Data that we wish to store.

Declaring an array of records (Pseudocode)

Python doesn’t require you to declare variables with types explicitly as it is a loosely typed language so in an exam situation if you were asked to store 40 BMI records using a design notation you could use:

Using an array of records in Pseudocode

DECLARE BMIDetails (39) AS BMI

BMIDetails[0].height = 1.6

BMIDetails[0].weight = 62.3

This stores the following data.

The second record ( element 1) is empty at the minute but is just there to remind us that we have an array of records.

We will now calculate the BMI and store it in the first record:

BMIDetails[0].BMI = BMIDetails[0].weight / (BMIDetails[0].height ^ 2)

We have used the height and weight fields to calculate the BMI for the first record so are now storing all of the data shown below:

Record 0 with BMI calculated

To insert the next record would use:

BMIDetails[1].height = 1.7

BMIDetails[1].weight = 73.3

BMIDetails[1].BMI = BMIDetails[1].weight / (BMIDetails[1].height ^ 2)

Record 1 now has values stored

Using an array of records in Python

Declares a dataclass called BMI ( not officially a record but is what we will use in Python. This is only available in Python 3.7 and above.

Declares an array of 40 BMI Records.

Assigns the values to the fields for the first records in element 0 of the myBMI Array and calculates the BMI.

Displays the details of the first record that we created.

Using a loop - Efficiency

It would be much more efficient to use a loop to create and populate an array of records.

In pseudocode it would look like:

DECLARE BMIDetails (39) AS BMI

FOR i = 0 to LENGTH(BMIDetails)

BMIDetails[i].height = GET INPUT FROM USER

BMIDetails[i].weight = GET INPUT FROM USER

BMIDetails[i].BMI = BMIDetails[i].height / (BMIDetails[i].weight ^ 2)

NEXT LOOP

And in Python:

Loops through for the length of the array and uses the loop counter x to place the values at the specified elements in the array.

Tutorial Video - Records

6 - Records.mp4

Next - String Handling

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