numpy-100是github上的一个项目,这是一套基于jupyter notebook针对numpy练习题,这套练习对于熟悉numpy非常有帮助,里面的题目也很实用,有兴趣的可以去github上clone下来。
1. Import the numpy package under the name np
(★☆☆)
1 | import numpy as np |
2. Print the numpy version and the configuration (★☆☆)
1 | print(np.__version__) |
3. Create a null vector of size 10 (★☆☆)
1 | Z = np.zeros(10) |
4. How to find the memory size of any array (★☆☆)
1 | Z = np.zeros((10,10)) |
5. How to get the documentation of the numpy add function from the command line? (★☆☆)
1 | %run `python -c "import numpy; numpy.info(numpy.add)"` |
6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆)
1 | Z = np.zeros(10) |
7. Create a vector with values ranging from 10 to 49 (★☆☆)
1 | Z = np.arange(10,50) |
8. Reverse a vector (first element becomes last) (★☆☆)
1 | Z = np.arange(50) |
9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆)
1 | Z = np.arange(9).reshape(3,3) |
10. Find indices of non-zero elements from [1,2,0,0,4,0] (★☆☆)
1 | nz = np.nonzero([1,2,0,0,4,0]) |
11. Create a 3x3 identity matrix (★☆☆)
1 | Z = np.eye(3) |
12. Create a 3x3x3 array with random values (★☆☆)
1 | Z = np.random.random((3,3,3)) |
13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆)
1 | Z = np.random.random((10,10)) |
14. Create a random vector of size 30 and find the mean value (★☆☆)
1 | Z = np.random.random(30) |
15. Create a 2d array with 1 on the border and 0 inside (★☆☆)
1 | Z = np.ones((10,10)) |
16. How to add a border (filled with 0’s) around an existing array? (★☆☆)
1 | Z = np.ones((5,5)) |
17. What is the result of the following expression? (★☆☆)
1 | print(0 * np.nan) |
18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆)
1 | Z = np.diag(1+np.arange(4),k=-1) |
19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆)
1 | Z = np.zeros((8,8),dtype=int) |
20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element?
1 | print(np.unravel_index(99,(6,7,8))) |
21. Create a checkerboard 8x8 matrix using the tile function (★☆☆)
1 | Z = np.tile( np.array([[0,1],[1,0]]), (4,4)) |
22. Normalize a 5x5 random matrix (★☆☆)
1 | Z = np.random.random((5,5)) |
23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆)
1 | color = np.dtype([("r", np.ubyte, 1), |
24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆)
1 | Z = np.dot(np.ones((5,3)), np.ones((3,2))) |
25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆)
1 | # Author: Evgeni Burovski |
26. What is the output of the following script? (★☆☆)
1 | # Author: Jake VanderPlas |
27. Consider an integer vector Z, which of these expressions are legal? (★☆☆)
1 | Z**Z |
28. What are the result of the following expressions?
1 | print(np.array(0) / np.array(0)) |
29. How to round away from zero a float array ? (★☆☆)
1 | # Author: Charles R Harris |
30. How to find common values between two arrays? (★☆☆)
1 | Z1 = np.random.randint(0,10,10) |
31. How to ignore all numpy warnings (not recommended)? (★☆☆)
1 | # Suicide mode on |
An equivalent way, with a context manager:
1 | with np.errstate(divide='ignore'): |
32. Is the following expressions true? (★☆☆)
1 | np.sqrt(-1) == np.emath.sqrt(-1) |
33. How to get the dates of yesterday, today and tomorrow? (★☆☆)
1 | yesterday = np.datetime64('today', 'D') - np.timedelta64(1, 'D') |
34. How to get all the dates corresponding to the month of July 2016? (★★☆)
1 | Z = np.arange('2016-07', '2016-08', dtype='datetime64[D]') |
35. How to compute ((A+B)*(-A/2)) in place (without copy)? (★★☆)
1 | A = np.ones(3)*1 |
36. Extract the integer part of a random array using 5 different methods (★★☆)
1 | Z = np.random.uniform(0,10,10) |
37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆)
1 | Z = np.zeros((5,5)) |
38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆)
1 | def generate(): |
39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆)
1 | Z = np.linspace(0,1,11,endpoint=False)[1:] |
40. Create a random vector of size 10 and sort it (★★☆)
1 | Z = np.random.random(10) |
41. How to sum a small array faster than np.sum? (★★☆)
1 | # Author: Evgeni Burovski |
42. Consider two random array A and B, check if they are equal (★★☆)
1 | A = np.random.randint(0,2,5) |
43. Make an array immutable (read-only) (★★☆)
1 | Z = np.zeros(10) |
44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆)
1 | Z = np.random.random((10,2)) |
45. Create random vector of size 10 and replace the maximum value by 0 (★★☆)
1 | Z = np.random.random(10) |
46. Create a structured array with x
and y
coordinates covering the [0,1]x[0,1] area (★★☆)
1 | Z = np.zeros((5,5), [('x',float),('y',float)]) |
47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj))
1 | # Author: Evgeni Burovski |
48. Print the minimum and maximum representable value for each numpy scalar type (★★☆)
1 | for dtype in [np.int8, np.int32, np.int64]: |
49. How to print all the values of an array? (★★☆)
1 | np.set_printoptions(threshold=np.nan) |
50. How to find the closest value (to a given scalar) in a vector? (★★☆)
1 | Z = np.arange(100) |
51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆)
1 | Z = np.zeros(10, [ ('position', [ ('x', float, 1), |
52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆)
1 | Z = np.random.random((10,2)) |
53. How to convert a float (32 bits) array into an integer (32 bits) in place?
1 | Z = np.arange(10, dtype=np.float32) |
54. How to read the following file? (★★☆)
1 | from io import StringIO |
55. What is the equivalent of enumerate for numpy arrays? (★★☆)
1 | Z = np.arange(9).reshape(3,3) |
56. Generate a generic 2D Gaussian-like array (★★☆)
1 | X, Y = np.meshgrid(np.linspace(-1,1,10), np.linspace(-1,1,10)) |
57. How to randomly place p elements in a 2D array? (★★☆)
1 | # Author: Divakar |
58. Subtract the mean of each row of a matrix (★★☆)
1 | # Author: Warren Weckesser |
59. How to I sort an array by the nth column? (★★☆)
1 | # Author: Steve Tjoa |
60. How to tell if a given 2D array has null columns? (★★☆)
1 | # Author: Warren Weckesser |
61. Find the nearest value from a given value in an array (★★☆)
1 | Z = np.random.uniform(0,1,10) |
62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆)
1 | A = np.arange(3).reshape(3,1) |
63. Create an array class that has a name attribute (★★☆)
1 | class NamedArray(np.ndarray): |
64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★)
1 | # Author: Brett Olsen |
65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★)
1 | # Author: Alan G Isaac |
66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★)
1 | # Author: Nadav Horesh |
67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★)
1 | A = np.random.randint(0,10,(3,4,3,4)) |
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? (★★★)
1 | # Author: Jaime Fernández del Río |
69. How to get the diagonal of a dot product? (★★★)
1 | # Author: Mathieu Blondel |
70. Consider the vector [1, 2, 3, 4, 5], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★)
1 | # Author: Warren Weckesser |
71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★)
1 | A = np.ones((5,5,3)) |
72. How to swap two rows of an array? (★★★)
1 | # Author: Eelco Hoogendoorn |
73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the triangles (★★★)
1 | # Author: Nicolas P. Rougier |
74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★)
1 | # Author: Jaime Fernández del Río |
75. How to compute averages using a sliding window over an array? (★★★)
1 | # Author: Jaime Fernández del Río |
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]) (★★★)
1 | # Author: Joe Kington / Erik Rigtorp |
77. How to negate a boolean, or to change the sign of a float inplace? (★★★)
1 | # Author: Nathaniel J. Smith |
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])? (★★★)
1 | def distance(P0, P1, p): |
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])? (★★★)
1 | # Author: Italmassov Kuanysh |
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) (★★★)
1 | # Author: Nicolas Rougier |
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]]? (★★★)
1 | # Author: Stefan van der Walt |
82. Compute a matrix rank (★★★)
1 | # Author: Stefan van der Walt |
83. How to find the most frequent value in an array?
1 | Z = np.random.randint(0,10,50) |
84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★)
1 | # Author: Chris Barker |
85. Create a 2D array subclass such that Z[i,j] == Z[j,i] (★★★)
1 | # Author: Eric O. Lebigot |
86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★)
1 | # Author: Stefan van der Walt |
87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★)
1 | # Author: Robert Kern |
88. How to implement the Game of Life using numpy arrays? (★★★)
1 | # Author: Nicolas Rougier |
89. How to get the n largest values of an array (★★★)
1 | Z = np.arange(10000) |
90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★)
1 | # Author: Stefan Van der Walt |
91. How to create a record array from a regular array? (★★★)
1 | Z = np.array([("Hello", 2.5, 3), |
92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★)
1 | # Author: Ryan G. |
93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★)
1 | # Author: Gabe Schwartz |
94. Considering a 10x3 matrix, extract rows with unequal values (e.g. [2,2,3]) (★★★)
1 | # Author: Robert Kern |
95. Convert a vector of ints into a matrix binary representation (★★★)
1 | # Author: Warren Weckesser |
96. Given a two dimensional array, how to extract unique rows? (★★★)
1 | # Author: Jaime Fernández del Río |
97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★)
1 | # Author: Alex Riley |
98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)?
1 | # Author: Bas Swinckels |
99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★)
1 | # Author: Evgeni Burovski |
100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★)
1 | # Author: Jessica B. Hamrick |