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Incredible trick on how to reshape to automatic value of dimension in Numpy

Posted on April 12, 2021March 2, 2023 By Luke K

Let’s learn how to reshape to automatic value of dimension in Numpy Python library.
Numpy automatic dimension reshape

Why you need the trick

You may need this trick when:

  • you don’t know the size of the base array
  • you expect base array to change size
  • you don’t know which value of dimension to put
  • See also  How to generate Cauchy Matrix from arrays in Numpy?

    The trick is:

    put -1 as a value!
    
    

    How to do the trick

    See the example code:

    import numpy as np
    my_array = np.random.random([6, 6])
    print(f'The original array: \n {my_array}')
    
    reshaped_array = my_array.reshape(2, -1, 3)
    print(f'The modified array: \n {reshaped_array}')
    
    

    As you can see I put reshape(2, -1, 3) and it worked. Numpy automatically guessed that it should be 6 instead of -1.

    See also  Correlation between arrays in Numpy

    Remember: you can use -1 only once!

    numpy Tags:array, dimension, reshape

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