100 Numpy Exercises With Hint

May 24, 2026 · 10 分钟阅读 · Python NumPy ·

title: "100 numpy exercises with hint" date: 2026-05-24T13:50:42Z

100 numpy exercises with hint

This is a collection of exercises that have been collected in the numpy mailing list, on stack overflow and in the numpy documentation. The goal of this collection is to offer a quick reference for both old and new users but also to provide a set of exercises for those who teach.

If you find an error or think you've a better way to solve some of them, feel free to open an issue at https://github.com/rougier/numpy-100

1. Import the numpy package under the name `np` (★☆☆)

(hint: import … as …)

2. Print the numpy version and the configuration (★☆☆)

(hint: np.__version__, np.show_config)

3. Create a null vector of size 10 (★☆☆)

(hint: np.zeros)

4. How to find the memory size of any array (★☆☆)

(hint: size, itemsize)

5. How to get the documentation of the numpy add function from the command line? (★☆☆)

(hint: np.info)

6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆)

(hint: array[4])

7. Create a vector with values ranging from 10 to 49 (★☆☆)

(hint: np.arange)

8. Reverse a vector (first element becomes last) (★☆☆)

(hint: array[::-1])

9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆)

(hint: reshape)

10. Find indices of non-zero elements from [1,2,0,0,4,0] (★☆☆)

(hint: np.nonzero)

11. Create a 3x3 identity matrix (★☆☆)

(hint: np.eye)

12. Create a 3x3x3 array with random values (★☆☆)

(hint: np.random.random)

13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆)

(hint: min, max)

14. Create a random vector of size 30 and find the mean value (★☆☆)

(hint: mean)

15. Create a 2d array with 1 on the border and 0 inside (★☆☆)

(hint: array[1:-1, 1:-1])

16. How to add a border (filled with 0's) around an existing array? (★☆☆)

(hint: np.pad)

17. What is the result of the following expression? (★☆☆)

(hint: NaN = not a number, inf = infinity)

10 * np.nan
2np.nan == np.nan
3np.inf > np.nan
4np.nan - np.nan
5np.nan in set([np.nan])
60.3 == 3 * 0.1

18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆)

(hint: np.diag)

19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆)

(hint: array[::2])

20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element?

(hint: np.unravel_index)

21. Create a checkerboard 8x8 matrix using the tile function (★☆☆)

(hint: np.tile)

22. Normalize a 5x5 random matrix (★☆☆)

(hint: (x - mean) / std)

23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆)

(hint: np.dtype)

24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆)

(hint: np.dot | @)

25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆)

(hint: >, <=)

26. What is the output of the following script? (★☆☆)

(hint: np.sum)

1# Author: Jake VanderPlas
2
3print(sum(range(5),-1))
4from numpy import *
5print(sum(range(5),-1))

27. Consider an integer vector Z, which of these expressions are legal? (★☆☆)

1Z**Z
22 << Z >> 2
3Z <- Z
41j*Z
5Z/1/1
6Z<Z>Z

28. What are the result of the following expressions?

1np.array(0) / np.array(0)
2np.array(0) // np.array(0)
3np.array([np.nan]).astype(int).astype(float)

29. How to round away from zero a float array ? (★☆☆)

(hint: np.uniform, np.copysign, np.ceil, np.abs)

30. How to find common values between two arrays? (★☆☆)

(hint: np.intersect1d)

31. How to ignore all numpy warnings (not recommended)? (★☆☆)

(hint: np.seterr, np.errstate)

32. Is the following expressions true? (★☆☆)

(hint: imaginary number)

1np.sqrt(-1) == np.emath.sqrt(-1)

33. How to get the dates of yesterday, today and tomorrow? (★☆☆)

(hint: np.datetime64, np.timedelta64)

34. How to get all the dates corresponding to the month of July 2016? (★★☆)

(hint: np.arange(dtype=datetime64['D']))

35. How to compute ((A+B)*(-A/2)) in place (without copy)? (★★☆)

(hint: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=))

36. Extract the integer part of a random array using 5 different methods (★★☆)

(hint: %, np.floor, np.ceil, astype, np.trunc)

37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆)

(hint: np.arange)

38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆)

(hint: np.fromiter)

39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆)

(hint: np.linspace)

40. Create a random vector of size 10 and sort it (★★☆)

(hint: sort)

41. How to sum a small array faster than np.sum? (★★☆)

(hint: np.add.reduce)

42. Consider two random array A and B, check if they are equal (★★☆)

(hint: np.allclose, np.array_equal)

43. Make an array immutable (read-only) (★★☆)

(hint: flags.writeable)

44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆)

(hint: np.sqrt, np.arctan2)

45. Create random vector of size 10 and replace the maximum value by 0 (★★☆)

(hint: argmax)

46. Create a structured array with `x` and `y` coordinates covering the [0,1]x[0,1] area (★★☆)

(hint: np.meshgrid)

47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj))

(hint: np.subtract.outer)

48. Print the minimum and maximum representable value for each numpy scalar type (★★☆)

(hint: np.iinfo, np.finfo, eps)

49. How to print all the values of an array? (★★☆)

(hint: np.set_printoptions)

50. How to find the closest value (to a given scalar) in a vector? (★★☆)

(hint: argmin)

51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆)

(hint: dtype)

52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆)

(hint: np.atleast_2d, T, np.sqrt)

53. How to convert a float (32 bits) array into an integer (32 bits) in place?

(hint: astype(copy=False))

54. How to read the following file? (★★☆)

(hint: np.genfromtxt)

11, 2, 3, 4, 5
26,  ,  , 7, 8
3 ,  , 9,10,11

55. What is the equivalent of enumerate for numpy arrays? (★★☆)

(hint: np.ndenumerate, np.ndindex)

56. Generate a generic 2D Gaussian-like array (★★☆)

(hint: np.meshgrid, np.exp)

57. How to randomly place p elements in a 2D array? (★★☆)

(hint: np.put, np.random.choice)

58. Subtract the mean of each row of a matrix (★★☆)

(hint: mean(axis=,keepdims=))

59. How to sort an array by the nth column? (★★☆)

(hint: argsort)

60. How to tell if a given 2D array has null columns? (★★☆)

(hint: any, ~)

61. Find the nearest value from a given value in an array (★★☆)

(hint: np.abs, argmin, flat)

62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆)

(hint: np.nditer)

63. Create an array class that has a name attribute (★★☆)

(hint: class method)

64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★)

(hint: np.bincount | np.add.at)

65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★)

(hint: np.bincount)

66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★)

(hint: np.unique)

67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★)

(hint: sum(axis=(-2,-1)))

68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset indices? (★★★)

(hint: np.bincount)

69. How to get the diagonal of a dot product? (★★★)

(hint: np.diag)

70. Consider the vector [1, 2, 3, 4, 5], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★)

(hint: array[::4])

71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★)

(hint: array[:, :, None])

72. How to swap two rows of an array? (★★★)

(hint: array[[]] = array[[]])

73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the triangles (★★★)

(hint: repeat, np.roll, np.sort, view, np.unique)

74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★)

(hint: np.repeat)

75. How to compute averages using a sliding window over an array? (★★★)

(hint: np.cumsum)

76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z[0],Z[1],Z[2]) and each subsequent row is shifted by 1 (last row should be (Z[-3],Z[-2],Z[-1]) (★★★)

(hint: from numpy.lib import stride_tricks)

77. How to negate a boolean, or to change the sign of a float inplace? (★★★)

(hint: np.logical_not, np.negative)

78. Consider 2 sets of points P0,P1 describing lines (2d) and a point p, how to compute distance from p to each line i (P0[i],P1[i])? (★★★)

79. Consider 2 sets of points P0,P1 describing lines (2d) and a set of points P, how to compute distance from each point j (P[j]) to each line i (P0[i],P1[i])? (★★★)

80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★)

(hint: minimum, maximum)

81. Consider an array Z = [1,2,3,4,5,6,7,8,9,10,11,12,13,14], how to generate an array R = [[1,2,3,4], [2,3,4,5], [3,4,5,6], ..., [11,12,13,14]]? (★★★)

(hint: stride_tricks.as_strided)

82. Compute a matrix rank (★★★)

(hint: np.linalg.svd) (suggestion: np.linalg.svd)

83. How to find the most frequent value in an array?

(hint: np.bincount, argmax)

84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★)