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| 1 | +# This file provides demo for numpy module |
| 2 | +import numpy as np |
| 3 | +import random |
| 4 | + |
| 5 | + |
| 6 | +def initialisation_demo(): |
| 7 | + # To create empty array |
| 8 | + arr = np.zeros(5, 'i') |
| 9 | + print("Empty arr: ", arr, " dtype:", arr.dtype, " dimension: ", arr.ndim) |
| 10 | + |
| 11 | + str_arr = np.zeros(5, "O") |
| 12 | + print("Empty string arr: ", str_arr, " dtype:", str_arr.dtype, " dimension: ", str_arr.ndim) |
| 13 | + |
| 14 | + arr = np.ones(5, 'i') |
| 15 | + print("Array with ones : ", arr, " dtype:", arr.dtype, " dimension: ", arr.ndim) |
| 16 | + |
| 17 | + str_arr = np.full(5, "Test", object) |
| 18 | + print("String arr with default values: ", str_arr, " dtype:", str_arr.dtype, " dimension: ", str_arr.ndim) |
| 19 | + |
| 20 | + zero_like_arr = np.zeros_like(arr) |
| 21 | + print("zero_like_arr: ", zero_like_arr, " dtype:", |
| 22 | + zero_like_arr.dtype, " dimension: ", zero_like_arr.ndim) |
| 23 | + |
| 24 | + one_like_arr = np.ones_like(str_arr, dtype='f', shape=2) |
| 25 | + print("one_like_arr: ", one_like_arr, " dtype:", one_like_arr.dtype, |
| 26 | + " dimension: ", one_like_arr.ndim) |
| 27 | + |
| 28 | + full_like_arr = np.full_like(one_like_arr, fill_value="Hi", dtype=object, shape=[1, 2]) |
| 29 | + print("full_like_arr: ", full_like_arr, " dtype:", full_like_arr.dtype, |
| 30 | + " dimension: ", full_like_arr.ndim) |
| 31 | + |
| 32 | + |
| 33 | +def one_dimensional_array(): |
| 34 | + num_list = random.sample(range(0, 100), 7) |
| 35 | + arr = np.array(num_list, 'i') |
| 36 | + print("Accessing elements using indexing of one dimensional array") |
| 37 | + for i in range(arr.size): |
| 38 | + print(f"arr[{i}]: {arr[i]}", end="\t") |
| 39 | + |
| 40 | + print("") |
| 41 | + print("Updating value at 2nd position to 39") |
| 42 | + arr[1] = 39 |
| 43 | + print("Post updating value at 2nd position: ", arr) |
| 44 | + |
| 45 | + print("Updating values at more than one position using slicing " |
| 46 | + " i.e. position 6 and 7 ") |
| 47 | + arr[5:7] = 29 |
| 48 | + print("Post updating value at 6th and 7th position: ", arr) |
| 49 | + |
| 50 | + print("Array from 2nd element till 7th element " |
| 51 | + "with skip = 2 " |
| 52 | + "using slicing: ", arr[1:6:2]) |
| 53 | + |
| 54 | + print("To access array using negative indexing ", arr[-3:]) |
| 55 | + |
| 56 | + print("To reverse array ", arr[::-1]) |
| 57 | + |
| 58 | + |
| 59 | +def two_dimensional_arr(): |
| 60 | + # empty array with zero values |
| 61 | + arr = np.zeros((2, 2), dtype='i') |
| 62 | + print("2-D array with zero values ", arr) |
| 63 | + |
| 64 | + # initialising array with values |
| 65 | + arr = np.array([[1, 2], [3, 4], [5, 6], [7, 8], [9, -1]], dtype='i') |
| 66 | + print("2-D array with initial values ", arr, " dimension: ", arr.ndim, |
| 67 | + " Data type: ", arr.dtype, " size of array: ", arr.size, |
| 68 | + "shape: ", arr.shape) |
| 69 | + |
| 70 | + # accessing elements using index |
| 71 | + print("element at 1st row and 2nd column: ", arr[1, 1]) |
| 72 | + |
| 73 | + # updating value at particular position |
| 74 | + print("update value at 1st row and 2nd column to 9") |
| 75 | + arr[1, 1] = 9 |
| 76 | + print("Array post updating element at 1st row and 2nd column") |
| 77 | + print(arr) |
| 78 | + |
| 79 | + # updating value at multiple position |
| 80 | + print("update value at 2nd row: 7") |
| 81 | + arr[2:3] = 7 |
| 82 | + print("Array post updating element at 3rd row") |
| 83 | + print(arr) |
| 84 | + |
| 85 | + new_arr = arr[1:4:2] |
| 86 | + # get 2-D array from existing one |
| 87 | + print("Getting new 2-D array from existing one using" |
| 88 | + "slicing", new_arr, " shape: ", new_arr.shape) |
| 89 | + |
| 90 | + new_arr = arr[1:4:2, 0:1] |
| 91 | + # get 2-D array from existing one with one column |
| 92 | + print("Getting new 2-D array with one column " |
| 93 | + "from existing one using" |
| 94 | + "slicing", new_arr, " shape: ", new_arr.shape) |
| 95 | + |
| 96 | + # reverse 2-D array |
| 97 | + print("Reverse 2-D array ", arr[::-1]) |
| 98 | + |
| 99 | + |
| 100 | +def copy_and_view_demo(): |
| 101 | + arr = np.array([1, 2, 3, 4], dtype=int) |
| 102 | + print("Original arr : ", arr, " base: ", arr.base) |
| 103 | + arr1 = arr.copy() |
| 104 | + print("Copied arr : ", arr1, " base: ", arr1.base) |
| 105 | + arr2 = arr.view() |
| 106 | + print("Viewed arr : ", arr2, " base: ", arr2.base) |
| 107 | + |
| 108 | + print("updating element at 1st index " |
| 109 | + "in copied array with value 5 and" |
| 110 | + "view with value 7") |
| 111 | + |
| 112 | + arr1[1] = 5 |
| 113 | + arr2[2] = 7 |
| 114 | + |
| 115 | + print("post update") |
| 116 | + print(f"original array: {arr}") |
| 117 | + print(f"Copied array: {arr1}") |
| 118 | + print(f"view: {arr2}") |
| 119 | + |
| 120 | + |
| 121 | +def shapeDemo(): |
| 122 | + arr = np.full((3, 2), 1, dtype='i') |
| 123 | + for i in arr: |
| 124 | + for j in i: |
| 125 | + print(j, end="\t") |
| 126 | + print("") |
| 127 | + |
| 128 | + |
| 129 | +def reShapeDemo(): |
| 130 | + |
| 131 | + num_list = random.sample(range(1, 100), 7) |
| 132 | + arr = np.array(num_list, dtype='i') |
| 133 | + print(f"Input array before resize: {arr} with shape: {arr.shape} and base: {arr.base}") |
| 134 | + |
| 135 | + try: |
| 136 | + reshaped_arr = np.reshape(arr, newshape=(2, 4)) |
| 137 | + |
| 138 | + except ValueError as v: |
| 139 | + print("Error received : ", v) |
| 140 | + print("Need to resize now input array !!!") |
| 141 | + |
| 142 | + arr = np.resize(arr, 8) |
| 143 | + print(f"Input array post resize: {arr} with shape: {arr.shape} and base: {arr.base}") |
| 144 | + |
| 145 | + reshaped_arr = np.reshape(arr, newshape=(2, 4)) |
| 146 | + print(f"Reshaped array with new shape: {reshaped_arr.shape} and base: {reshaped_arr.base}") |
| 147 | + for i in reshaped_arr: |
| 148 | + for j in i: |
| 149 | + print(j, end="\t") |
| 150 | + print("") |
| 151 | + |
| 152 | + finally: |
| 153 | + print("-"*50) |
| 154 | + |
| 155 | +def reShapeDemo2(): |
| 156 | + arr = np.array([[1, 2, 3], [4, 5, 6]], dtype='i') |
| 157 | + print(f"Input array before reshape: {arr} with shape: {arr.shape} and base: {arr.base}") |
| 158 | + arr1 = arr.flatten() |
| 159 | + arr2 = arr.ravel() |
| 160 | + print("Flatten existing array: ", arr1, " with base: ", arr1.base) |
| 161 | + print("ravel existing array: ", arr2, " with base: ", arr2.base) |
| 162 | + |
| 163 | + |
| 164 | +def itrDemo(): |
| 165 | + arr = np.array([[1, 2, 3], [4, 5, 6]], dtype='i') |
| 166 | + for x in np.nditer(arr[::, :2], flags=['buffered'], op_dtypes='S'): |
| 167 | + print(x) |
| 168 | + |
| 169 | +def joinDemo(): |
| 170 | + arr1 = np.array([1, 2, 3, 4, 5], dtype='i') |
| 171 | + arr2 = np.array([7, 8, 9, 10, 11], dtype='i') |
| 172 | + |
| 173 | + # using concatenate |
| 174 | + print(np.concatenate((arr1, arr2))) |
| 175 | + |
| 176 | + # using stack |
| 177 | + print(np.stack((arr1, arr2), axis=1)) |
| 178 | + |
| 179 | + # using hstack |
| 180 | + print(np.hstack((arr1, arr2))) |
| 181 | + |
| 182 | + # using vstack |
| 183 | + print(np.vstack((arr1, arr2))) |
| 184 | + |
| 185 | +def main(): |
| 186 | + print("Version of numpy", np.__version__) |
| 187 | + reShapeDemo() |
| 188 | + |
| 189 | + |
| 190 | +if __name__ == "__main__": |
| 191 | + main() |
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