Hands-on exercise – Array Operations

Put the lesson Array Operations into practice by writing a program yourself.

Exercise field

Strong and light

The problem

You have the density (g/cm³) and yield strength (MPa) of six alloys. Specific strength, strength divided by density, measures how strong a material is for its weight.

Calculate it for every alloy at once, then find the alloys with a specific strength above 100.

Your program should

Calculate the specific strength of all six alloys with one expression.
Use a Boolean mask to print the names of alloys with a specific strength above 100.
Print their specific strengths rounded to 1 decimal place with np.round().

Expected output

['Al 6061' 'Al 7075' 'Ti-6Al-4V' 'Mg AZ31']
[102.2 179.  198.6 113. ]

Your solution

Write your program below and press Run. Each run is checked against the expected output.

main.py

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Output

Press Run to see what your program prints.

Need help?

One possible solution. Other programs that print the same output are correct too.

solution.py

import numpy as npnames = np.array(["Al 6061", "Al 7075", "Ti-6Al-4V", "Steel 1020", "Mg AZ31", "Cu C11000"])density = np.array([2.70, 2.81, 4.43, 7.87, 1.77, 8.96])     # g/cm³yield_strength = np.array([276, 503, 880, 350, 200, 70])      # MPaspecific = yield_strength / densityis_strong = specific > 100print(names[is_strong])print(np.round(specific[is_strong], 1))

Output

['Al 6061' 'Al 7075' 'Ti-6Al-4V' 'Mg AZ31'] [102.2 179. 198.6 113. ]