NumPy: From given student name, height, and class sort by class, then height if class are equal
3. Structured Array Sorted by Class Then Height
Write a NumPy program to create a structured array from given student name, height, class and their data types. Now sort by class, then height if class are equal.
Sample Solution:
Python Code:
# Importing the NumPy library
import numpy as np
# Defining the data types for the structured array
data_type = [('name', 'S15'), ('class', int), ('height', float)]
# Defining the details of students as a list of tuples
students_details = [('James', 5, 48.5), ('Nail', 6, 52.5), ('Paul', 5, 42.10), ('Pit', 5, 40.11)]
# Creating a structured array 'students' using the defined data type and provided details
students = np.array(students_details, dtype=data_type)
# Displaying the original structured array
print("Original array:")
print(students)
# Sorting the structured array by 'class' and 'height' fields
print("Sort by class, then height if class are equal:")
print(np.sort(students, order=['class', 'height']))
Sample Output:
Original array: [(b'James', 5, 48.5 ) (b'Nail', 6, 52.5 ) (b'Paul', 5, 42.1 ) (b'Pit', 5, 40.11)] Sort by class, then height if class are equal: [(b'Pit', 5, 40.11) (b'Paul', 5, 42.1 ) (b'James', 5, 48.5 ) (b'Nail', 6, 52.5 )]
Explanation:
In the above code -
data_type = [('name', 'S15'), ('class', int), ('height', float)]: This line defines a custom data type data_type with three fields: 'name' (a string with a maximum length of 15 characters), 'class' (an integer), and 'height' (a float).
students_details = [('James', 5, 48.5), ('Nail', 6, 52.5),('Paul', 5, 42.10), ('Pit', 5, 40.11)]: This line creates a list of tuples, where each tuple contains student details (name, class, and height).
students = np.array(students_details, dtype=data_type): This line creates a structured Numpy array of students using the custom data type data_type. It assigns students_details elements to the corresponding fields in the array.
print(np.sort(students, order=['class', 'height'])): This line sorts the students array based on two fields: 'class' and 'height'. The sorting is done first by the 'class' field in ascending order. For records with the same 'class' value, sorting is done by the 'height' field in ascending order. The sorted array is then printed.
Pictorial Presentation:
For more Practice: Solve these Related Problems:
- Sort a structured array by the 'class' field first, then by the 'height' field when classes are equal, using np.sort with multiple keys.
- Implement a stable sort that first sorts by height and then re-sorts by class to maintain the relative order for equal classes.
- Create a function that allows sorting by multiple fields and returns the sorted array for a given order tuple.
- Test the multi-key sort on an array where several students share the same class to verify correct secondary ordering by height.
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Next: Write a NumPy program to sort the student id with increasing height of the students from given students id and height. Print the integer indices that describes the sort order by multiple columns and the sorted data.
Python-Numpy Code Editor:
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