Numpy

Numpy Library Doc in Bangla

• numpy basic
  • 1d array
  • 2d array
  • 3d array
  • NumPy Ndarray Properties
  • NumPy Constants
  • Martix
  • .empty()
  • .eye()
  • identity matrix
  • ones matrix
  • zeroes matrix
  • .full()
  • Matrix creation routines
  • .tri()
  • tril() and triu()
  • random methods
  • random.randint()
  • random.rand()
  • Array Manipulation Routines
  • .arange()
  • .reshape()
  • .array()
  • .flatten()
  • .ravel()
  • .stack()
  • .split()
  • .flip()
  • rot90()
  • .roll()
  • bitwise operators
  • median, average, std, mean, variance, histogram
  • Numpy writing , save and reading files
  • Reading the data from a CSV file
  • Set Operations
  • .unique()
  • .in1d()
  • .intersect1d() , .setdiff1d() , .setxor1d() , .union1d()
  • Sorting with NumPy
  • Count Non Zero Element
• numpy Advance
• 100 numpy exercises
  • 1. Import the numpy package under the name np (★☆☆)
  • 2. Print the numpy version and the configuration (★☆☆)
  • 3. Create a null vector of size 10 (★☆☆)
  • 4. How to find the memory size of any array (★☆☆)
  • 5. How to get the documentation of the numpy add function from the command line? (★☆☆)
  • 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆)
  • 7. Create a vector with values ranging from 10 to 49 (★☆☆)
  • 8. Reverse a vector (first element becomes last) (★☆☆)
  • 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆)
  • 10. Find indices of non-zero elements from [1,2,0,0,4,0] (★☆☆)
  • 11. Create a 3x3 identity matrix (★☆☆)
  • 12. Create a 3x3x3 array with random values (★☆☆)
  • 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆)
  • 14. Create a random vector of size 30 and find the mean value (★☆☆)
  • 15. Create a 2d array with 1 on the border and 0 inside (★☆☆)
  • 16. How to add a border (filled with 0’s) around an existing array? (★☆☆)
  • 17. What is the result of the following expression? (★☆☆)
  • 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆)
  • 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆)
  • 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element?
  • 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆)
  • 22. Normalize a 5x5 random matrix (★☆☆)
  • 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆)
  • 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆)
  • 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆)
  • 26. What is the output of the following script? (★☆☆)
  • 27. Consider an integer vector Z, which of these expressions are legal? (★☆☆)
  • 28. What are the result of the following expressions?
  • 29. How to round away from zero a float array ? (★☆☆)
  • 30. How to find common values between two arrays? (★☆☆)
  • 31. How to ignore all numpy warnings (not recommended)? (★☆☆)
  • 32. Is the following expressions true? (★☆☆)
  • 33. How to get the dates of yesterday, today and tomorrow? (★☆☆)
  • 34. How to get all the dates corresponding to the month of July 2016? (★★☆)
  • 35. How to compute ((A+B)*(-A/2)) in place (without copy)? (★★☆)
  • 36. Extract the integer part of a random array of positive numbers using 4 different methods (★★☆)
  • 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆)
  • 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆)
  • 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆)
  • 40. Create a random vector of size 10 and sort it (★★☆)
  • 41. How to sum a small array faster than np.sum? (★★☆)
  • 42. Consider two random array A and B, check if they are equal (★★☆)
  • 43. Make an array immutable (read-only) (★★☆)
  • 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆)
  • 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆)
  • 46. Create a structured array with x and y coordinates covering the [0,1]x[0,1] area (★★☆)
  • 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj))
  • 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆)
  • 49. How to print all the values of an array? (★★☆)
  • 50. How to find the closest value (to a given scalar) in a vector? (★★☆)
  • 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆)
  • 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆)
  • 53. How to convert a float (32 bits) array into an integer (32 bits) in place?
  • 54. How to read the following file? (★★☆)
  • 55. What is the equivalent of enumerate for numpy arrays? (★★☆)
  • 56. Generate a generic 2D Gaussian-like array (★★☆)
  • 57. How to randomly place p elements in a 2D array? (★★☆)
  • 58. Subtract the mean of each row of a matrix (★★☆)
  • 59. How to sort an array by the nth column? (★★☆)
  • 60. How to tell if a given 2D array has null columns? (★★☆)
  • 61. Find the nearest value from a given value in an array (★★☆)
  • 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆)
  • 63. Create an array class that has a name attribute (★★☆)
  • 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★)
  • 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★)
  • 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★)
  • 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★)
  • 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? (★★★)
  • 69. How to get the diagonal of a dot product? (★★★)
  • 70. Consider the vector [1, 2, 3, 4, 5], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★)
  • 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★)
  • 72. How to swap two rows of an 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 (★★★)
  • 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★)
  • 75. How to compute averages using a sliding window over an array? (★★★)
  • 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]) (★★★)
  • 77. How to negate a boolean, or to change the sign of a float inplace? (★★★)
  • 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) (★★★)
  • 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]]? (★★★)
  • 82. Compute a matrix rank (★★★)
  • 83. How to find the most frequent value in an array?
  • 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★)
  • 85. Create a 2D array subclass such that Z[i,j] == Z[j,i] (★★★)
  • 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)) (★★★)
  • 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★)
  • 88. How to implement the Game of Life using numpy arrays? (★★★)
  • 89. How to get the n largest values of an array (★★★)
  • 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★)
  • 91. How to create a record array from a regular array? (★★★)
  • 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★)
  • 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? (★★★)
  • 94. Considering a 10x3 matrix, extract rows with unequal values (e.g. [2,2,3]) (★★★)
  • 95. Convert a vector of ints into a matrix binary representation (★★★)
  • 96. Given a two dimensional array, how to extract unique rows? (★★★)
  • 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★)
  • 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)?
  • 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. (★★★)
  • 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). (★★★)
• 100 numpy exercises with hints
  • 1. Import the numpy package under the name np (★☆☆)
  • 2. Print the numpy version and the configuration (★☆☆)
  • 3. Create a null vector of size 10 (★☆☆)
  • 4. How to find the memory size of any array (★☆☆)
  • 5. How to get the documentation of the numpy add function from the command line? (★☆☆)
  • 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆)
  • 7. Create a vector with values ranging from 10 to 49 (★☆☆)
  • 8. Reverse a vector (first element becomes last) (★☆☆)
  • 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆)
  • 10. Find indices of non-zero elements from [1,2,0,0,4,0] (★☆☆)
  • 11. Create a 3x3 identity matrix (★☆☆)
  • 12. Create a 3x3x3 array with random values (★☆☆)
  • 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆)
  • 14. Create a random vector of size 30 and find the mean value (★☆☆)
  • 15. Create a 2d array with 1 on the border and 0 inside (★☆☆)
  • 16. How to add a border (filled with 0’s) around an existing array? (★☆☆)
  • 17. What is the result of the following expression? (★☆☆)
  • 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆)
  • 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆)
  • 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element?
  • 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆)
  • 22. Normalize a 5x5 random matrix (★☆☆)
  • 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆)
  • 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆)
  • 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆)
  • 26. What is the output of the following script? (★☆☆)
  • 27. Consider an integer vector Z, which of these expressions are legal? (★☆☆)
  • 28. What are the result of the following expressions?
  • 29. How to round away from zero a float array ? (★☆☆)
  • 30. How to find common values between two arrays? (★☆☆)
  • 31. How to ignore all numpy warnings (not recommended)? (★☆☆)
  • 32. Is the following expressions true? (★☆☆)
  • 33. How to get the dates of yesterday, today and tomorrow? (★☆☆)
  • 34. How to get all the dates corresponding to the month of July 2016? (★★☆)
  • 35. How to compute ((A+B)*(-A/2)) in place (without copy)? (★★☆)
  • 36. Extract the integer part of a random array of positive numbers using 4 different methods (★★☆)
  • 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆)
  • 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆)
  • 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆)
  • 40. Create a random vector of size 10 and sort it (★★☆)
  • 41. How to sum a small array faster than np.sum? (★★☆)
  • 42. Consider two random array A and B, check if they are equal (★★☆)
  • 43. Make an array immutable (read-only) (★★☆)
  • 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆)
  • 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆)
  • 46. Create a structured array with x and y coordinates covering the [0,1]x[0,1] area (★★☆)
  • 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj))
  • 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆)
  • 49. How to print all the values of an array? (★★☆)
  • 50. How to find the closest value (to a given scalar) in a vector? (★★☆)
  • 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆)
  • 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆)
  • 53. How to convert a float (32 bits) array into an integer (32 bits) in place?
  • 54. How to read the following file? (★★☆)
  • 55. What is the equivalent of enumerate for numpy arrays? (★★☆)
  • 56. Generate a generic 2D Gaussian-like array (★★☆)
  • 57. How to randomly place p elements in a 2D array? (★★☆)
  • 58. Subtract the mean of each row of a matrix (★★☆)
  • 59. How to sort an array by the nth column? (★★☆)
  • 60. How to tell if a given 2D array has null columns? (★★☆)
  • 61. Find the nearest value from a given value in an array (★★☆)
  • 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆)
  • 63. Create an array class that has a name attribute (★★☆)
  • 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★)
  • 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★)
  • 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★)
  • 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★)
  • 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? (★★★)
  • 69. How to get the diagonal of a dot product? (★★★)
  • 70. Consider the vector [1, 2, 3, 4, 5], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★)
  • 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★)
  • 72. How to swap two rows of an 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 (★★★)
  • 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★)
  • 75. How to compute averages using a sliding window over an array? (★★★)
  • 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]) (★★★)
  • 77. How to negate a boolean, or to change the sign of a float inplace? (★★★)
  • 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) (★★★)
  • 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]]? (★★★)
  • 82. Compute a matrix rank (★★★)
  • 83. How to find the most frequent value in an array?
  • 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★)
  • 85. Create a 2D array subclass such that Z[i,j] == Z[j,i] (★★★)
  • 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)) (★★★)
  • 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★)
  • 88. How to implement the Game of Life using numpy arrays? (★★★)
  • 89. How to get the n largest values of an array (★★★)
  • 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★)
  • 91. How to create a record array from a regular array? (★★★)
  • 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★)
  • 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? (★★★)
  • 94. Considering a 10x3 matrix, extract rows with unequal values (e.g. [2,2,3]) (★★★)
  • 95. Convert a vector of ints into a matrix binary representation (★★★)
  • 96. Given a two dimensional array, how to extract unique rows? (★★★)
  • 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★)
  • 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)?
  • 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. (★★★)
  • 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). (★★★)
• 100 numpy exercises with solutions
  • 1. Import the numpy package under the name np (★☆☆)
  • 2. Print the numpy version and the configuration (★☆☆)
  • 3. Create a null vector of size 10 (★☆☆)
  • 4. How to find the memory size of any array (★☆☆)
  • 5. How to get the documentation of the numpy add function from the command line? (★☆☆)
  • 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆)
  • 7. Create a vector with values ranging from 10 to 49 (★☆☆)
  • 8. Reverse a vector (first element becomes last) (★☆☆)
  • 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆)
  • 10. Find indices of non-zero elements from [1,2,0,0,4,0] (★☆☆)
  • 11. Create a 3x3 identity matrix (★☆☆)
  • 12. Create a 3x3x3 array with random values (★☆☆)
  • 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆)
  • 14. Create a random vector of size 30 and find the mean value (★☆☆)
  • 15. Create a 2d array with 1 on the border and 0 inside (★☆☆)
  • 16. How to add a border (filled with 0’s) around an existing array? (★☆☆)
  • 17. What is the result of the following expression? (★☆☆)
  • 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆)
  • 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆)
  • 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element?
  • 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆)
  • 22. Normalize a 5x5 random matrix (★☆☆)
  • 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆)
  • 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆)
  • 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆)
  • 26. What is the output of the following script? (★☆☆)
  • 27. Consider an integer vector Z, which of these expressions are legal? (★☆☆)
  • 28. What are the result of the following expressions?
  • 29. How to round away from zero a float array ? (★☆☆)
  • 30. How to find common values between two arrays? (★☆☆)
  • 31. How to ignore all numpy warnings (not recommended)? (★☆☆)
  • 32. Is the following expressions true? (★☆☆)
  • 33. How to get the dates of yesterday, today and tomorrow? (★☆☆)
  • 34. How to get all the dates corresponding to the month of July 2016? (★★☆)
  • 35. How to compute ((A+B)*(-A/2)) in place (without copy)? (★★☆)
  • 36. Extract the integer part of a random array of positive numbers using 4 different methods (★★☆)
  • 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆)
  • 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆)
  • 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆)
  • 40. Create a random vector of size 10 and sort it (★★☆)
  • 41. How to sum a small array faster than np.sum? (★★☆)
  • 42. Consider two random array A and B, check if they are equal (★★☆)
  • 43. Make an array immutable (read-only) (★★☆)
  • 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆)
  • 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆)
  • 46. Create a structured array with x and y coordinates covering the [0,1]x[0,1] area (★★☆)
  • 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj))
  • 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆)
  • 49. How to print all the values of an array? (★★☆)
  • 50. How to find the closest value (to a given scalar) in a vector? (★★☆)
  • 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆)
  • 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆)
  • 53. How to convert a float (32 bits) array into an integer (32 bits) in place?
  • 54. How to read the following file? (★★☆)
  • 55. What is the equivalent of enumerate for numpy arrays? (★★☆)
  • 56. Generate a generic 2D Gaussian-like array (★★☆)
  • 57. How to randomly place p elements in a 2D array? (★★☆)
  • 58. Subtract the mean of each row of a matrix (★★☆)
  • 59. How to sort an array by the nth column? (★★☆)
  • 60. How to tell if a given 2D array has null columns? (★★☆)
  • 61. Find the nearest value from a given value in an array (★★☆)
  • 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆)
  • 63. Create an array class that has a name attribute (★★☆)
  • 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★)
  • 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★)
  • 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★)
  • 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★)
  • 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? (★★★)
  • 69. How to get the diagonal of a dot product? (★★★)
  • 70. Consider the vector [1, 2, 3, 4, 5], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★)
  • 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★)
  • 72. How to swap two rows of an 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 (★★★)
  • 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★)
  • 75. How to compute averages using a sliding window over an array? (★★★)
  • 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]) (★★★)
  • 77. How to negate a boolean, or to change the sign of a float inplace? (★★★)
  • 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) (★★★)
  • 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]]? (★★★)
  • 82. Compute a matrix rank (★★★)
  • 83. How to find the most frequent value in an array?
  • 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★)
  • 85. Create a 2D array subclass such that Z[i,j] == Z[j,i] (★★★)
  • 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)) (★★★)
  • 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★)
  • 88. How to implement the Game of Life using numpy arrays? (★★★)
  • 89. How to get the n largest values of an array (★★★)
  • 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★)
  • 91. How to create a record array from a regular array? (★★★)
  • 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★)
  • 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? (★★★)
  • 94. Considering a 10x3 matrix, extract rows with unequal values (e.g. [2,2,3]) (★★★)
  • 95. Convert a vector of ints into a matrix binary representation (★★★)
  • 96. Given a two dimensional array, how to extract unique rows? (★★★)
  • 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★)
  • 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)?
  • 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. (★★★)
  • 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). (★★★)
• 100 numpy exercises solutions with hints
  • 1. Import the numpy package under the name np (★☆☆)
  • 2. Print the numpy version and the configuration (★☆☆)
  • 3. Create a null vector of size 10 (★☆☆)
  • 4. How to find the memory size of any array (★☆☆)
  • 5. How to get the documentation of the numpy add function from the command line? (★☆☆)
  • 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆)
  • 7. Create a vector with values ranging from 10 to 49 (★☆☆)
  • 8. Reverse a vector (first element becomes last) (★☆☆)
  • 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆)
  • 10. Find indices of non-zero elements from [1,2,0,0,4,0] (★☆☆)
  • 11. Create a 3x3 identity matrix (★☆☆)
  • 12. Create a 3x3x3 array with random values (★☆☆)
  • 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆)
  • 14. Create a random vector of size 30 and find the mean value (★☆☆)
  • 15. Create a 2d array with 1 on the border and 0 inside (★☆☆)
  • 16. How to add a border (filled with 0’s) around an existing array? (★☆☆)
  • 17. What is the result of the following expression? (★☆☆)
  • 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆)
  • 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆)
  • 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element?
  • 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆)
  • 22. Normalize a 5x5 random matrix (★☆☆)
  • 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆)
  • 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆)
  • 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆)
  • 26. What is the output of the following script? (★☆☆)
  • 27. Consider an integer vector Z, which of these expressions are legal? (★☆☆)
  • 28. What are the result of the following expressions?
  • 29. How to round away from zero a float array ? (★☆☆)
  • 30. How to find common values between two arrays? (★☆☆)
  • 31. How to ignore all numpy warnings (not recommended)? (★☆☆)
  • 32. Is the following expressions true? (★☆☆)
  • 33. How to get the dates of yesterday, today and tomorrow? (★☆☆)
  • 34. How to get all the dates corresponding to the month of July 2016? (★★☆)
  • 35. How to compute ((A+B)*(-A/2)) in place (without copy)? (★★☆)
  • 36. Extract the integer part of a random array of positive numbers using 4 different methods (★★☆)
  • 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆)
  • 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆)
  • 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆)
  • 40. Create a random vector of size 10 and sort it (★★☆)
  • 41. How to sum a small array faster than np.sum? (★★☆)
  • 42. Consider two random array A and B, check if they are equal (★★☆)
  • 43. Make an array immutable (read-only) (★★☆)
  • 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆)
  • 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆)
  • 46. Create a structured array with x and y coordinates covering the [0,1]x[0,1] area (★★☆)
  • 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj))
  • 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆)
  • 49. How to print all the values of an array? (★★☆)
  • 50. How to find the closest value (to a given scalar) in a vector? (★★☆)
  • 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆)
  • 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆)
  • 53. How to convert a float (32 bits) array into an integer (32 bits) in place?
  • 54. How to read the following file? (★★☆)
  • 55. What is the equivalent of enumerate for numpy arrays? (★★☆)
  • 56. Generate a generic 2D Gaussian-like array (★★☆)
  • 57. How to randomly place p elements in a 2D array? (★★☆)
  • 58. Subtract the mean of each row of a matrix (★★☆)
  • 59. How to sort an array by the nth column? (★★☆)
  • 60. How to tell if a given 2D array has null columns? (★★☆)
  • 61. Find the nearest value from a given value in an array (★★☆)
  • 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆)
  • 63. Create an array class that has a name attribute (★★☆)
  • 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★)
  • 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★)
  • 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★)
  • 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★)
  • 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? (★★★)
  • 69. How to get the diagonal of a dot product? (★★★)
  • 70. Consider the vector [1, 2, 3, 4, 5], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★)
  • 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★)
  • 72. How to swap two rows of an 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 (★★★)
  • 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★)
  • 75. How to compute averages using a sliding window over an array? (★★★)
  • 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]) (★★★)
  • 77. How to negate a boolean, or to change the sign of a float inplace? (★★★)
  • 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) (★★★)
  • 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]]? (★★★)
  • 82. Compute a matrix rank (★★★)
  • 83. How to find the most frequent value in an array?
  • 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★)
  • 85. Create a 2D array subclass such that Z[i,j] == Z[j,i] (★★★)
  • 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)) (★★★)
  • 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★)
  • 88. How to implement the Game of Life using numpy arrays? (★★★)
  • 89. How to get the n largest values of an array (★★★)
  • 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★)
  • 91. How to create a record array from a regular array? (★★★)
  • 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★)
  • 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? (★★★)
  • 94. Considering a 10x3 matrix, extract rows with unequal values (e.g. [2,2,3]) (★★★)
  • 95. Convert a vector of ints into a matrix binary representation (★★★)
  • 96. Given a two dimensional array, how to extract unique rows? (★★★)
  • 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★)
  • 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)?
  • 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. (★★★)
  • 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). (★★★)