NumPy: Insert a new axis at the beginning in two arrays and combine the two into one

NumPy: Array Object Exercise-194 with Solution

Write a NumPy program to create two arrays with shape (300,400, 5), fill values using unsigned integer (0 to 255). Insert a new axis that will appear at the beginning in the expanded array shape. Now combine the said two arrays into one.

Sample Solution:

Python Code:

# Importing NumPy library
import numpy as np 

# Generating random arrays of integers from 0 to 255 with dimensions (200, 300, 3)
nums1 = np.random.randint(low=0, high=256, size=(200, 300, 3), dtype=np.uint8)
nums2 = np.random.randint(low=0, high=256, size=(200, 300, 3), dtype=np.uint8)

# Printing the original arrays
print("Array1:")
print(nums1)
print("\nArray2:")
print(nums2)

# Adding a new axis to the arrays along the 0th dimension
nums1 = np.expand_dims(nums1, axis=0)
nums2 = np.expand_dims(nums2, axis=0)

# Appending the arrays along the 0th axis
nums = np.append(nums1, nums2, axis=0)

# Printing the combined array
print("\nCombined array:")
print(nums)

Sample Output:

Array1:
[[[ 46 117  73]
  [215  90  86]
  [ 80  89 220]
  ...
  [ 47  94 234]
  [ 95  72  61]
  [154  91 175]]

 [[232 194  26]
  [219 116 116]
  [126 179 177]
  ...
  [247 216  60]
  [ 21  38  31]
  [187 117  92]]

 [[250 162 194]
  [111 157 112]
  [120  38  90]
  ...
  [195  45  31]
  [108  73  76]
  [176 189  76]]

 ...

 [[  5  98 255]
  [155  90 230]
  [231  74   8]
  ...
  [144  87  53]
  [242 204 189]
  [ 89  18  75]]

 [[ 18 169  99]
  [183   0 215]
  [ 10 141 208]
  ...
  [ 58 130 180]
  [225  47 173]
  [  6  64 215]]

 [[199 139  25]
  [207  63  18]
  [  0 163 176]
  ...
  [ 91  25 210]
  [ 10  31 201]
  [  2 116  82]]]

Array2:
[[[ 37  10 228]
  [241  52  82]
  [196  47 189]
  ...
  [127  70 246]
  [158  46  12]
  [ 56 129 162]]

 [[224 215  47]
  [139  72  13]
  [218  64  78]
  ...
  [171 108  55]
  [197  49  94]
  [ 24 108  48]]

 [[200 136  23]
  [160 248 212]
  [217 150 183]
  ...
  [216 217 159]
  [253 190  27]
  [130  79 140]]

 ...

 [[ 61  96 157]
  [ 19 201  53]
  [ 62 105 156]
  ...
  [ 24  13  37]
  [ 92  27 157]
  [106 109 164]]

 [[241  75  33]
  [210 118  79]
  [ 59 227 193]
  ...
  [208 187  55]
  [109 115 254]
  [115 134  68]]

 [[158 106 165]
  [189  48  54]
  [  5  84  26]
  ...
  [131 235  25]
  [101 146  90]
  [216  15  92]]]

Combined array:
[[[[ 46 117  73]
   [215  90  86]
   [ 80  89 220]
   ...
   [ 47  94 234]
   [ 95  72  61]
   [154  91 175]]

  [[232 194  26]
   [219 116 116]
   [126 179 177]
   ...
   [247 216  60]
   [ 21  38  31]
   [187 117  92]]

  [[250 162 194]
   [111 157 112]
   [120  38  90]
   ...
   [195  45  31]
   [108  73  76]
   [176 189  76]]

  ...

  [[  5  98 255]
   [155  90 230]
   [231  74   8]
   ...
   [144  87  53]
   [242 204 189]
   [ 89  18  75]]

  [[ 18 169  99]
   [183   0 215]
   [ 10 141 208]
   ...
   [ 58 130 180]
   [225  47 173]
   [  6  64 215]]

  [[199 139  25]
   [207  63  18]
   [  0 163 176]
   ...
   [ 91  25 210]
   [ 10  31 201]
   [  2 116  82]]]


 [[[ 37  10 228]
   [241  52  82]
   [196  47 189]
   ...
   [127  70 246]
   [158  46  12]
   [ 56 129 162]]

  [[224 215  47]
   [139  72  13]
   [218  64  78]
   ...
   [171 108  55]
   [197  49  94]
   [ 24 108  48]]

  [[200 136  23]
   [160 248 212]
   [217 150 183]
   ...
   [216 217 159]
   [253 190  27]
   [130  79 140]]

  ...

  [[ 61  96 157]
   [ 19 201  53]
   [ 62 105 156]
   ...
   [ 24  13  37]
   [ 92  27 157]
   [106 109 164]]

  [[241  75  33]
   [210 118  79]
   [ 59 227 193]
   ...
   [208 187  55]
   [109 115 254]
   [115 134  68]]

  [[158 106 165]
   [189  48  54]
   [  5  84  26]
   ...
   [131 235  25]
   [101 146  90]
   [216  15  92]]]]

Explanation:

In the above code -

nums1 and nums2: Create two random (200, 300, 3) arrays with integer values between 0 and 255, using the np.random.randint function. The dtype is set to np.uint8 to represent 8-bit color channels.

np.expand_dims(nums1, axis=0) and np.expand_dims(nums2, axis=0): Add an extra dimension to each of the arrays, nums1 and nums2, along the 0th axis. This converts their shapes from (200, 300, 3) to (1, 200, 300, 3).

np.append(nums1, nums2, axis=0): Concatenate the two arrays with expanded dimensions along the 0th axis. This creates a new array “nums” with the shape (2, 200, 300, 3), containing both images.

print(nums): Finally print() function prints the resulting array "nums".

Python-Numpy Code Editor:

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