Mastering NumPy: 100 Exercises with solutions for Python numerical computing

Last update on January 19 2024 12:46:56 (UTC/GMT +8 hours)

NumPy: Exercise-100 with Solution

Welcome to w3resource's 100 NumPy exercises collection! This comprehensive set of exercises is designed to help you master the fundamentals of NumPy, a powerful numerical computing library in Python. Whether you're a beginner or an experienced user looking to improve your skills, these exercises cover a wide range of topics. They provide practical challenges to enhance your NumPy understanding.

Exercise 1:

Create a 1D array with values ranging from 0 to 9.

import numpy as np
arr = np.arange(10)
print(arr)

[0 1 2 3 4 5 6 7 8 9]

Exercise 2:

Convert a 1D array to a 2D array with 2 rows.

import numpy as np
arr = np.arange(10).reshape(2, -1)
print(arr)

[[0 1 2 3 4]
 [5 6 7 8 9]]

Exercise 3:

Multiply a 5x3 matrix by a 3x2 matrix.

import numpy as np
mat1 = np.random.random((5, 3))
mat2 = np.random.random((3, 2))
result = np.dot(mat1, mat2)
print(result)

[[1.05787846 0.32439392]
 [2.18241234 0.68182548]
 [1.23629853 0.39596044]
 [0.42973189 0.12403945]
 [1.08039539 0.36356378]]

Exercise 4:

Extract all odd numbers from an array of 1-10.

import numpy as np
arr = np.arange(1, 11)
odd_numbers = arr[arr % 2 != 0]
print(odd_numbers)

[1 3 5 7 9]

Exercise 5:

Replace all odd numbers in an array of 1-10 with -1.

import numpy as np
arr = np.arange(1, 10)
arr[arr % 2 != 0] = -1
print(arr)

[-1  2 -1  4 -1  6 -1  8 -1]

Exercise 6:

Convert a 1D array to a boolean array where all positive values become True.

import numpy as np
arr = np.array([-1, 2, 0, -4, 5])
boolean_arr = arr > 0
print(boolean_arr)

[False  True False False  True]

Exercise 7:

Replace all even numbers in a 1D array with their negative.

import numpy as np
arr = np.arange(1, 10)
arr[arr % 2 == 0] *= -1
print(arr)

[ 1 -2  3 -4  5 -6  7 -8  9]

Exercise 8:

Create a random 3x3 matrix and normalize it.

import numpy as np
matrix = np.random.random((3,3))
normalized_matrix = (matrix - np.mean(matrix)) / np.std(matrix)
print(normalized_matrix)

[[ 1.07755282 -0.27940552 -1.57739216]
 [ 1.53962723  1.25274094 -0.97454418]
 [-0.30801978 -0.26192698 -0.46863236]]

Exercise 9:

Calculate the sum of the diagonal elements of a 3x3 matrix.

import numpy as np
matrix = np.random.random((3, 3))
diagonal_sum = np.trace(matrix)
print(diagonal_sum)

1.0183501284750802

Exercise 10:

Find the indices of non-zero elements from [1,2,0,0,4,0].

import numpy as np
arr = np.array([1, 2, 0, 0, 4, 0])
non_zero_indices = np.nonzero(arr)
print(non_zero_indices)

(array([0, 1, 4], dtype=int64),)

Exercise 11:

Reverse a 1D array (first element becomes the last).

import numpy as np
arr = np.arange(10)
reversed_arr = np.flip(arr)
print(reversed_arr)

[9 8 7 6 5 4 3 2 1 0]

Exercise 12:

Create a 3x3 identity matrix.

import numpy as np
identity_matrix = np.eye(3)
print(identity_matrix)

[[1. 0. 0.]
 [0. 1. 0.]
 [0. 0. 1.]]

Exercise 13:

Reshape a 1D array to a 2D array with 5 rows and 2 columns.

import numpy as np
arr = np.arange(10)
reshaped_arr = arr.reshape(5, 2)
print(reshaped_arr)

[[0 1]
 [2 3]
 [4 5]
 [6 7]
 [8 9]]

Exercise 14:

Stack two arrays vertically.

import numpy as np
arr1 = np.array([1, 2, 3])
arr2 = np.array([4, 5, 6])
stacked_arr = np.vstack((arr1, arr2))
print(stacked_arr)

[[1 2 3]
 [4 5 6]]

Exercise 15:

Get the common items between two arrays.

import numpy as np
arr1 = np.array([1, 2, 3, 4, 5])
arr2 = np.array([3, 4, 5, 6, 7])
common_items = np.intersect1d(arr1, arr2)
print(common_items)

[3 4 5]

Exercise 16:

Create a 5x5 matrix with row values ranging from 0 to 4.

import numpy as np
matrix = np.zeros((5, 5))
matrix += np.arange(5)
print(matrix)

[[0. 1. 2. 3. 4.]
 [0. 1. 2. 3. 4.]
 [0. 1. 2. 3. 4.]
 [0. 1. 2. 3. 4.]
 [0. 1. 2. 3. 4.]]

Exercise 17:

Find the index of the maximum value in a 1D array.

import numpy as np
arr = np.array([3, 7, 1, 10, 4])
max_index = np.argmax(arr)
print(max_index)

Exercise 18:

Normalize the values in a 1D array between 0 and 1.

import numpy as np
arr = np.array([2, 5, 10, 3, 8])
normalized_arr = (arr - np.min(arr)) / (np.max(arr) - np.min(arr))
print(normalized_arr)

[0.    0.375 1.    0.125 0.75 ]

Exercise 19:

Calculate the dot product of two arrays.

import numpy as np
arr1 = np.array([1, 2, 3])
arr2 = np.array([4, 5, 6])
dot_product = np.dot(arr1, arr2)
print(dot_product)

Exercise 20:

Count the number of elements in an array within a specific range.

import numpy as np
arr = np.array([2, 5, 8, 10, 12, 15])
count_within_range = np.sum((arr >= 5) & (arr <= 12))
print(count_within_range)

Exercise 21:

Find the mean of each row in a 2D array.

import numpy as np
matrix = np.random.random((3, 4))
row_means = np.mean(matrix, axis=1)
print(row_means)

[0.437043   0.73541944 0.45005375]

Exercise 22:

Create a random 4x4 matrix and extract the diagonal elements.

import numpy as np
matrix = np.random.random((4, 4))
diagonal_elements = np.diag(matrix)
print(diagonal_elements)

[0.3968107  0.3355669  0.91924761 0.907174  ]

Exercise 23:

Count the number of occurrences of a specific value in an array.

import numpy as np
arr = np.array([1, 2, 3, 4, 2, 3, 2, 1])
count_of_2 = np.count_nonzero(arr == 2)
print(count_of_2)

Exercise 24:

Replace all values in a 1D array with the mean of the array.

import numpy as np
arr = np.array([10, 20, 30, 40, 50])
arr[:] = np.mean(arr)
print(arr)

[30 30 30 30 30]

Exercise 25:

Find the indices of the maximum and minimum values in a 1D array.

import numpy as np
arr = np.array([5, 2, 8, 1, 7])
max_index = np.argmax(arr)
min_index = np.argmin(arr)
print("Index of max:", max_index)
print("Index of min:", min_index)

Index of max: 2
Index of min: 3

Exercise 26:

Create a 2D array with 1 on the border and 0 inside.

import numpy as np
arr = np.ones((5, 5))
arr[1:-1, 1:-1] = 0
print(arr)

[[1. 1. 1. 1. 1.]
 [1. 0. 0. 0. 1.]
 [1. 0. 0. 0. 1.]
 [1. 0. 0. 0. 1.]
 [1. 1. 1. 1. 1.]]

Exercise 27:

Find the unique values and their counts in a 1D array.

import numpy as np
arr = np.array([1, 2, 3, 2, 4, 1, 5, 4, 6])
unique_values, counts = np.unique(arr, return_counts=True)
print("Unique values:", unique_values)
print("Counts:", counts)

Unique values: [1 2 3 4 5 6]
Counts: [2 2 1 2 1 1]

Exercise 28:

Create a 3x3 matrix with values ranging from 0 to 8.

import numpy as np
matrix = np.arange(9).reshape(3, 3)
print(matrix)

[[0 1 2]
 [3 4 5]
 [6 7 8]]

Exercise 29:

Calculate the exponential of all elements in a 1D array.

import numpy as np
arr = np.array([1, 2, 3, 4, 5])
exponential_arr = np.exp(arr)
print(exponential_arr)

[  2.71828183   7.3890561   20.08553692  54.59815003 148.4131591 ]

Exercise 30:

Swap two rows in a 2D array.

import numpy as np
matrix = np.random.random((3, 4))
matrix[[0, 1]] = matrix[[1, 0]]
print(matrix)

[[0.64447186 0.98641154 0.7336092  0.79829912]
 [0.00753743 0.65414365 0.74147161 0.14819561]
 [0.53158903 0.89859906 0.75709264 0.49165449]]

Exercise 31:

Create a random 3x3 matrix and replace all values greater than 0.5 with 1 and all others with 0.

import numpy as np
matrix = np.random.random((3, 3))
matrix[matrix > 0.5] = 1
matrix[matrix <= 0.5] = 0
print(matrix)

[[1. 0. 1.]
 [0. 0. 0.]
 [0. 0. 0.]]

Exercise 32:

Find the indices of the top N maximum values in a 1D array.

import numpy as np
arr = np.array([10, 5, 8, 20, 15])
top_indices = np.argsort(arr)[-2:]  # Replace 2 with desired top N
print(top_indices)

[4 3]

Exercise 33:

Calculate the mean of each column in a 2D array.

import numpy as np
matrix = np.random.random((4, 3))
column_means = np.mean(matrix, axis=0)
print(column_means)

[0.54904302 0.4902671  0.42925161]

Exercise 34:

Normalize the values in each column of a 2D array.

import numpy as np
matrix = np.random.random((4, 3))
normalized_matrix = (matrix - np.mean(matrix, axis=0)) / np.std(matrix, axis=0)
print(normalized_matrix)

[[-0.46748521 -0.77417852 -0.84330049]
 [ 1.0967056   1.71309044  0.71160507]
 [ 0.7764295  -0.58168559  1.24351291]
 [-1.4056499  -0.35722632 -1.11181749]]

Exercise 35:

Concatenate two 1D arrays.

import numpy as np
arr1 = np.array([1, 2, 3])
arr2 = np.array([4, 5, 6])
concatenated_arr = np.concatenate((arr1, arr2))
print(concatenated_arr)

[1 2 3 4 5 6]

Exercise 36:

Create a 2D array with random values and sort each row.

import numpy as np
matrix = np.random.random((3, 4))
sorted_matrix = np.sort(matrix, axis=1)
print(sorted_matrix)

[[0.10858953 0.71557663 0.7986983  0.90525131]
 [0.318373   0.50887498 0.51900254 0.7860126 ]
 [0.06242782 0.12665803 0.12884579 0.1440853 ]]

Exercise 37:

Compute the mean squared error between two arrays.

import numpy as np
arr1 = np.array([1, 2, 3, 4])
arr2 = np.array([2, 3, 4, 5])
mse = np.mean((arr1 - arr2) ** 2)
print(mse)

1.0

Exercise 38:

Replace all negative values in an array with 0.

import numpy as np
arr = np.array([-1, 2, -3, 4, -5])
arr[arr < 0] = 0
print(arr)

[0 2 0 4 0]

Exercise 39:

Find the 5th and 95th percentiles of an array.

import numpy as np
arr = np.random.random(10)
percentile_5th = np.percentile(arr, 5)
percentile_95th = np.percentile(arr, 95)
print("5th Percentile:", percentile_5th)
print("95th Percentile:", percentile_95th)

5th Percentile: 0.04785597751800983
95th Percentile: 0.8708086577975086

Exercise 40:

Create a random 2x2 matrix and compute its determinant.

import numpy as np
matrix = np.random.random((2, 2))
determinant = np.linalg.det(matrix)
print(determinant)

0.0019446951056262907

Exercise 41:

Count the number of elements in an array that are greater than the mean.

import numpy as np
arr = np.array([1, 2, 3, 4, 5])
count_above_mean = np.sum(arr > np.mean(arr))
print(count_above_mean)

Exercise 42:

Calculate the square root of each element in a 1D array.

import numpy as np
arr = np.array([4, 9, 16, 25])
sqrt_arr = np.sqrt(arr)
print(sqrt_arr)

[2. 3. 4. 5.]

Exercise 43:

Create a 3x3 matrix and compute the matrix square root.

import numpy as np
matrix = np.random.random((3, 3))
matrix_sqrt = np.linalg.matrix_power(matrix, 2)
print(matrix_sqrt)

[[0.62607741 0.64326801 0.24778017]
 [1.35236384 1.43972006 0.56587005]
 [0.617024   0.71519995 0.29469311]]

Exercise 44:

Convert the data type of an array to float.

import numpy as np
arr = np.array([1, 2, 3, 4], dtype=int)
float_arr = arr.astype(float)
print(float_arr)

[1. 2. 3. 4.]

Exercise 45:

Calculate the element-wise absolute values of an array.

import numpy as np
arr = np.array([-1, -2, 3, -4])
abs_values = np.abs(arr)
print(abs_values)

[1 2 3 4]

Exercise 46:

Find the indices where elements of two arrays match.

import numpy as np
arr1 = np.array([1, 2, 3, 4, 5])
arr2 = np.array([3, 2, 8, 4, 5])
matching_indices = np.where(arr1 == arr2)
print(matching_indices)

(array([1, 3, 4], dtype=int64),)

Exercise 47:

Calculate the cumulative sum of elements in a 1D array.

import numpy as np
arr = np.array([1, 2, 3, 4, 5])
cumulative_sum = np.cumsum(arr)
print(cumulative_sum)

[ 1  3  6 10 15]

Exercise 48:

Compute the inverse of a 2x2 matrix.

import numpy as np
matrix = np.random.random((2, 2))
inverse_matrix = np.linalg.inv(matrix)
print(inverse_matrix)

[[ 1.22685384 -4.14864181]
 [-0.2704788   6.62123806]]

Exercise 49:

Count the number of non-zero elements in a 2D array.

import numpy as np
matrix = np.array([[0, 1, 0], [2, 0, 3], [0, 4, 0]])
non_zero_count = np.count_nonzero(matrix)
print(non_zero_count)

Exercise 50:

Create a 2D array and replace all nan values with 0.

import numpy as np
matrix = np.array([[1, np.nan, 3], [4, 5, np.nan], [7, 8, 9]])
matrix[np.isnan(matrix)] = 0
print(matrix)

[[1. 0. 3.]
 [4. 5. 0.]
 [7. 8. 9.]]

Exercise 51:

Find the correlation coefficient between two arrays.

import numpy as np
arr1 = np.array([1, 2, 3, 4, 5])
arr2 = np.array([3, 4, 5, 6, 7])
correlation_coefficient = np.corrcoef(arr1, arr2)[0, 1]
print(correlation_coefficient)

0.9999999999999999

Exercise 52:

Create a 1D array and remove all duplicate values.

import numpy as np
arr = np.array([1, 2, 3, 2, 4, 5, 1])
unique_arr = np.unique(arr)
print(unique_arr)

[1 2 3 4 5]

Exercise 53:

Compute the element-wise product of two arrays.

import numpy as np
arr1 = np.array([1, 2, 3])
arr2 = np.array([4, 5, 6])
elementwise_product = np.multiply(arr1, arr2)
print(elementwise_product)

[ 4 10 18]

Exercise 54:

Calculate the standard deviation of each column in a 2D array.

import numpy as np
matrix = np.random.random((4, 3))
column_stddev = np.std(matrix, axis=0)
print(column_stddev)

[0.22702366 0.27411548 0.25568707]

Exercise 55:

Create a 2D array and set all values above a certain threshold to that threshold.

import numpy as np
matrix = np.random.random((3, 4))
threshold = 0.7
matrix[matrix > threshold] = threshold
print(matrix)

[[0.7        0.54918234 0.7        0.01893358]
 [0.09114833 0.00268936 0.13766009 0.28160436]
 [0.40448374 0.7        0.7        0.30830747]]

Exercise 56:

Create a random 5x5 matrix and replace the maximum value by -1.

import numpy as np
matrix = np.random.random((5, 5))
max_value_index = np.unravel_index(np.argmax(matrix), matrix.shape)
matrix[max_value_index] = -1
print(matrix)

[[ 0.45916565  0.79856137  0.68998918  0.04439129  0.84814684]
 [ 0.4442666   0.2661443   0.83980951  0.71727557  0.30334519]
 [ 0.47332068  0.50437988  0.51222628  0.65334221  0.21664521]
 [ 0.7511065   0.77837283  0.29019334  0.82695944  0.41608473]
 [ 0.23775068  0.07539172 -1.          0.14166163  0.56071446]]

Exercise 57:

Convert a 1D array of Fahrenheit temperatures to Celsius.

import numpy as np
fahrenheit_temps = np.array([32, 68, 100, 212])
celsius_temps = (fahrenheit_temps - 32) * 5/9
print(celsius_temps)

[  0.          20.          37.77777778 100.        ]

Exercise 58:

Compute the outer product of two arrays.

import numpy as np
arr1 = np.array([1, 2, 3])
arr2 = np.array([4, 5, 6])
outer_product = np.outer(arr1, arr2)
print(outer_product)

[[ 4  5  6]
 [ 8 10 12]
 [12 15 18]]

Exercise 59:

Create a 1D array with 10 equidistant values between 0 and 1.

import numpy as np
equidistant_arr = np.linspace(0, 1, 10)
print(equidistant_arr)

[0.         0.11111111 0.22222222 0.33333333 0.44444444 0.55555556
 0.66666667 0.77777778 0.88888889 1.        ]

Exercise 60:

Compute the cross product of two 3D arrays.

import numpy as np
arr1 = np.array([1, 2, 3])
arr2 = np.array([4, 5, 6])
cross_product = np.cross(arr1, arr2)
print(cross_product)

[-3 6 -3]

Exercise 61:

Calculate the percentile along a specific axis of a 2D array.

import numpy as np
matrix = np.random.random((3, 4))
percentiles_axis1 = np.percentile(matrix, 75, axis=1)
print(percentiles_axis1)

[0.73954718 0.63159296 0.49097014]

Exercise 62:

Create a 1D array and add a border of 0s around it.

import numpy as np
arr = np.array([1, 2, 3, 4])
arr_with_border = np.pad(arr, (1, 1), mode='constant', constant_values=0)
print(arr_with_border)

[0 1 2 3 4 0]

Exercise 63:

Compute the histogram of a 1D array.

import numpy as np
arr = np.array([1, 1, 2, 2, 2, 3, 3, 3, 3])
hist, bins = np.histogram(arr, bins=[1, 2, 3, 4])
print("Histogram:", hist)
print("Bin edges:", bins)

Histogram: [2 3 4]
Bin edges: [1 2 3 4]

Exercise 64:

Create a 2D array with random values and normalize each row.

import numpy as np
matrix = np.random.random((4, 3))
normalized_rows = matrix / np.linalg.norm(matrix, axis=1, keepdims=True)
print(normalized_rows)

[[0.61881278 0.58433001 0.52500398]
 [0.50152886 0.39533452 0.76953195]
 [0.18399814 0.89840062 0.39877439]
 [0.76636647 0.25223155 0.59081442]]

Exercise 65:

Create a random 2D array and sort it by the second column.

import numpy as np
matrix = np.random.random((3, 4))
sorted_matrix_by_column2 = matrix[matrix[:, 1].argsort()]
print(sorted_matrix_by_column2)

[[0.28214407 0.30234856 0.56159219 0.34651641]
 [0.72579465 0.64605243 0.14824549 0.6364958 ]
 [0.4852539  0.96161675 0.41756529 0.7079494 ]]

Exercise 66:

Calculate the determinant of a 3x3 matrix.

import numpy as np
matrix = np.random.random((3, 3))
determinant = np.linalg.det(matrix)
print(determinant)

0.09550080558000806

Exercise 67:

Calculate the element-wise exponentiation of a 1D array.

import numpy as np
arr = np.array([2, 3, 4])
exponentiated_arr = np.exp(arr)
print(exponentiated_arr)

[ 7.3890561  20.08553692 54.59815003]

Exercise 68:

Calculate the Frobenius norm of a 2D array.

import numpy as np
matrix = np.random.random((3, 4))
frobenius_norm = np.linalg.norm(matrix)
print(frobenius_norm)

1.8692600488600242

Exercise 69:

Create a 2D array with random values and replace the maximum value with the minimum.

import numpy as np
matrix = np.random.random((3, 4))
max_value_index = np.unravel_index(np.argmax(matrix), matrix.shape)
min_value = np.min(matrix)
matrix[max_value_index] = min_value
print(matrix)

[[0.29383093 0.01637657 0.7794734  0.01637657]
 [0.76911564 0.22745882 0.32986131 0.84500937]
 [0.94922056 0.54607467 0.80921816 0.28474546]]

Exercise 70:

Compute the matrix multiplication of two 2D arrays.

import numpy as np
matrix1 = np.random.random((3, 4))
matrix2 = np.random.random((4, 5))
matrix_multiplication = np.dot(matrix1, matrix2)
print(matrix_multiplication)

[[0.99119942 0.85513185 0.57664501 0.31851386 0.84601174]
 [1.38306551 1.16773145 0.83001893 0.68922723 1.12666608]
 [1.72827308 1.44430652 1.03782659 1.28492828 1.24906297]]

Exercise 71:

Create a 1D array and set the values between 10 and 20 to 0.

import numpy as np
arr = np.array([5, 15, 12, 18, 25])
arr[(arr >= 10) & (arr <= 20)] = 0
print(arr)

[ 5  0  0  0 25]

Exercise 72:

Compute the inverse hyperbolic sine of each element in a 1D array.

import numpy as np
arr = np.array([1, 2, 3, 4])
inverse_sineh_arr = np.arcsinh(arr)
print(inverse_sineh_arr)

[0.88137359 1.44363548 1.81844646 2.09471255]

Exercise 73:

Compute the Kronecker product of two arrays.

import numpy as np
arr1 = np.array([1, 2])
arr2 = np.array([3, 4])
kronecker_product = np.kron(arr1, arr2)
print(kronecker_product)

[3 4 6 8]

Exercise 74:

Calculate the mean absolute deviation of a 1D array.

import numpy as np
arr = np.array([1, 2, 3, 4, 5])
mean_absolute_deviation = np.mean(np.abs(arr - np.mean(arr)))
print(mean_absolute_deviation)

1.2

Exercise 75:

Create a 3x3 matrix and set all values above the main diagonal to zero.

import numpy as np
matrix = np.random.random((3, 3))
matrix[np.triu_indices(3, 1)] = 0
print(matrix)

[[0.7344708  0.         0.        ]
 [0.91154103 0.58004909 0.        ]
 [0.53953411 0.73231191 0.8315308 ]]

Exercise 76:

Count the number of occurrences of each unique value in a 1D array.

import numpy as np
arr = np.array([2, 2, 1, 3, 3, 3, 4])
unique_values, counts = np.unique(arr, return_counts=True)
print("Unique values:", unique_values)
print("Counts:", counts)

Unique values: [1 2 3 4]
Counts: [1 2 3 1]

Exercise 77:

Compute the cumulative product of elements along a given axis in a 2D array.

import numpy as np
matrix = np.random.random((3, 4))
cumulative_product_axis0 = np.cumprod(matrix, axis=0)
print(cumulative_product_axis0)

[[0.65005294 0.01951926 0.25636043 0.30961964]
 [0.28738887 0.00883133 0.24993819 0.06504888]
 [0.21895124 0.00590692 0.0116853  0.03512077]]

Exercise 78:

Round elements of a 1D array to the nearest integer.

import numpy as np
arr = np.array([1.2, 2.7, 3.5, 4.9])
rounded_arr = np.round(arr)
print(rounded_arr)

[1. 3. 4. 5.]

Exercise 79:

Create a 1D array and append a new element to the end.

import numpy as np
arr = np.array([1, 2, 3])
new_element = 4
arr = np.append(arr, new_element)
print(arr)

[1 2 3 4]

Exercise 80:

Calculate the element-wise absolute difference between two arrays.

import numpy as np
arr1 = np.array([3, 7, 1, 10, 4])
arr2 = np.array([2, 5, 8, 1, 7])
absolute_difference = np.abs(arr1 - arr2)
print(absolute_difference)

[1 2 7 9 3]

Exercise 81:

Create a 2D array with random values and replace the maximum value in each row with -1.

import numpy as np
matrix = np.random.random((3, 4))
max_values_indices = np.argmax(matrix, axis=1)
matrix[np.arange(matrix.shape[0]), max_values_indices] = -1
print(matrix)

[[ 0.14015869  0.13279371 -1.          0.4665563 ]
 [ 0.73795369  0.311774   -1.          0.05087541]
 [ 0.6516183  -1.          0.30233177  0.48674956]]

Exercise 82:

Normalize the columns of a 2D array to have a sum of 1.

import numpy as np
matrix = np.random.random((3, 4))
normalized_columns = matrix / np.sum(matrix, axis=0, keepdims=True)
print(normalized_columns)

[[0.00548299 0.49881449 0.16102029 0.23643045]
 [0.58935257 0.27548946 0.54365728 0.57390056]
 [0.40516443 0.22569604 0.29532244 0.18966899]]

Exercise 83:

Find the indices of the top N minimum values in a 1D array.

import numpy as np
arr = np.array([10, 5, 8, 1, 7])
top_indices = np.argsort(arr)[:2]  # Replace 2 with desired top N
print(top_indices)

[3 1]

Exercise 84:

Convert the elements of a 1D array to strings.

import numpy as np
arr = np.array([1, 2, 3, 4])
string_arr = arr.astype(str)
print(string_arr)

['1' '2' '3' '4']

Exercise 85:

Compute the percentile rank of each element in a 1D array.

import numpy as np
from scipy.stats import percentileofscore
arr = np.array([1, 2, 3, 4, 5])
# Calculate percentile rank for each element in arr
percentile_rank = np.array([percentileofscore(arr, value) for value in arr])
print(percentile_rank)

[ 20.  40.  60.  80. 100.]

Exercise 86:

Create a 1D array and shuffle its elements randomly.

import numpy as np
arr = np.array([1, 2, 3, 4, 5])
np.random.shuffle(arr)
print(arr)

[4 2 5 1 3]

Exercise 87:

Check if all elements in a 1D array are non-zero.

import numpy as np
arr = np.array([1, 2, 3, 4, 5])
all_nonzero = np.all(arr != 0)
print(all_nonzero)

True

Exercise 88:

Find the indices of the maximum value in each row of a 2D array.

import numpy as np
matrix = np.random.random((3, 4))
max_indices_per_row = np.argmax(matrix, axis=1)
print(max_indices_per_row)

[1 3 2]

Exercise 89:

Create a 2D array and replace all nan values with the mean of the array.

import numpy as np
matrix = np.array([[1, np.nan, 3], [4, 5, np.nan], [7, 8, 9]])
nan_mean = np.nanmean(matrix)
matrix[np.isnan(matrix)] = nan_mean
print(matrix)

[[1.         5.28571429 3.        ]
 [4.         5.         5.28571429]
 [7.         8.         9.        ]]

Exercise 90:

Calculate the mean of each row in a 2D array ignoring nan values.

import numpy as np
matrix = np.array([[1, 2, np.nan], [4, np.nan, 6], [7, 8, 9]])
row_means_ignore_nan = np.nanmean(matrix, axis=1)
print(row_means_ignore_nan)

[1.5 5.  8. ]

Exercise 91:

Compute the sum of diagonal elements in a 2D array.

import numpy as np
matrix = np.random.random((3, 3))
diagonal_sum = np.trace(matrix)
print(diagonal_sum)

1.375162416021255

Exercise 92:

Convert radians to degrees for each element in a 1D array.

import numpy as np
arr_in_radians = np.array([np.pi/2, np.pi, 3*np.pi/2])
arr_in_degrees = np.degrees(arr_in_radians)
print(arr_in_degrees)

[ 90. 180. 270.]

Exercise 93:

Calculate the pairwise Euclidean distance between two arrays.

import numpy as np
arr1 = np.array([1, 2, 3])
arr2 = np.array([4, 5, 6])
euclidean_distance = np.linalg.norm(arr1 - arr2)
print(euclidean_distance)

5.196152422706632

Exercise 94:

Create a 1D array and set the values between the 25th and 75th percentile to 0.

import numpy as np
arr = np.array([10, 20, 30, 40, 50])
percentile_25th = np.percentile(arr, 25)
percentile_75th = np.percentile(arr, 75)
arr[(arr >= percentile_25th) & (arr <= percentile_75th)] = 0
print(arr)

[10  0  0  0 50]

Exercise 95:

Calculate the element-wise square of the difference between two arrays.

import numpy as np
arr1 = np.array([1, 2, 3])
arr2 = np.array([4, 5, 6])
squared_difference = (arr1 - arr2)**2
print(squared_difference)

[9 9 9]

Exercise 96:

Replace all even numbers in a 1D array with the next odd number.

import numpy as np
arr = np.array([2, 5, 8, 12, 15])
arr[arr % 2 == 0] += 1
print(arr)

[ 3  5  9 13 15]

Exercise 97:

Create a 2D array and normalize each column by its range..

import numpy as np
matrix = np.random.random((3, 4))
normalized_columns_range = (matrix - np.min(matrix, axis=0)) / (np.max(matrix, axis=0) - np.min(matrix, axis=0))
print(normalized_columns_range)

[[0.         1.         0.         1.        ]
 [0.38748809 0.         1.         0.        ]
 [1.         0.39378719 0.83348354 0.78448847]]

Exercise 98:

Compute the cumulative sum of elements along a given axis in a 2D array.

import numpy as np
matrix = np.random.random((3, 4))
cumulative_sum_axis1 = np.cumsum(matrix, axis=1)
print(cumulative_sum_axis1)

[[0.23623571 0.76181793 1.40183102 2.02358543]
 [0.89415619 1.38540147 1.46977913 1.99923603]
 [0.3626984  0.94484957 1.24671758 2.19056585]]

Exercise 99:

Check if any element in a 1D array is non-zero.

import numpy as np
arr = np.array([0, 0, 0, 1, 0])
any_nonzero = np.any(arr != 0)
print(any_nonzero)

True

Exercise 100:

Create a 2D array with random integers and replace all values greater than a certain threshold with that threshold.

import numpy as np
matrix = np.random.randint(0, 100, size=(3, 4))
threshold = 75
matrix[matrix > threshold] = threshold
print(matrix)

[[72 55 56 26]
 [ 8 16 54 75]
 [13 74 36 75]]

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