Accessing fields by name in NumPy - Mini Project: Build & Apply

Accessing Fields by Name in NumPy Structured Arrays

📖 Scenario: You work in a small store and keep track of products using a table with columns for product name, price, and quantity.

🎯 Goal: You will create a structured NumPy array to store product data, then access the price field by its name to see the prices of all products.

📋 What You'll Learn

Create a NumPy structured array with fields 'name', 'price', and 'quantity'.

Use a configuration variable to select the field name 'price'.

Access the 'price' field from the structured array using the field name.

Print the prices of all products.

💡 Why This Matters

🌍 Real World

Stores and businesses often keep product data in tables with named columns. Accessing fields by name helps quickly get specific information like prices or quantities.

💼 Career

Data scientists and analysts use structured arrays or tables to organize data. Knowing how to access fields by name is essential for data cleaning, analysis, and reporting.

1

Create a NumPy structured array with product data

Import NumPy as np. Create a structured array called products with three entries. Each entry should have fields: 'name' (string of length 10), 'price' (float), and 'quantity' (integer). Use these exact values: ('apple', 0.5, 10), ('banana', 0.3, 20), ('orange', 0.8, 15).

NumPy

import numpy as np
# Create the structured array 'products' with the specified fields and values
# Your code here

Need a hint?

Use np.array with a list of tuples and specify dtype as a list of tuples with field names and types.

2

Set a variable for the field name to access

Create a variable called field_name and set it to the string 'price'. This will help us select the price field later.

NumPy

import numpy as np
products = np.array([
    ('apple', 0.5, 10),
    ('banana', 0.3, 20),
    ('orange', 0.8, 15)
], dtype=[('name', 'U10'), ('price', 'f4'), ('quantity', 'i4')])
# Create the variable 'field_name' and set it to 'price'
# Your code here

Need a hint?

Just assign the string 'price' to the variable field_name.

3

Access the price field using the field name variable

Use the variable field_name to access the price field from the products array. Store the result in a variable called prices.

NumPy

import numpy as np
products = np.array([
    ('apple', 0.5, 10),
    ('banana', 0.3, 20),
    ('orange', 0.8, 15)
], dtype=[('name', 'U10'), ('price', 'f4'), ('quantity', 'i4')])
field_name = 'price'
# Access the 'price' field using 'field_name' and store it in 'prices'
# Your code here

Need a hint?

Use products[field_name] to get the array of prices.

4

Print the prices of all products

Print the variable prices to display the prices of all products.

NumPy

import numpy as np
products = np.array([
    ('apple', 0.5, 10),
    ('banana', 0.3, 20),
    ('orange', 0.8, 15)
], dtype=[('name', 'U10'), ('price', 'f4'), ('quantity', 'i4')])
field_name = 'price'
prices = products[field_name]
# Print the prices
# Your code here

Need a hint?

Use print(prices) to show the prices.