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How to replace one column by a value in a numpy array?

Hello Guys, How are you all? Hope You all Are Fine. Today We Are Going To learn about How to replace one column by a value in a numpy array in Python. So Here I am Explain to you all the possible Methods here.

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Table of Contents

How to replace one column by a value in a numpy array?

  1. How to replace one column by a value in a numpy array?

    Here a[:, 0] means “select all rows from column 0”. The value 1 is broadcast across this selected column, producing the desired array (it's not necessary to use a list [1, 1], although you can).

  2. replace one column by a value in a numpy array

    Here a[:, 0] means “select all rows from column 0”. The value 1 is broadcast across this selected column, producing the desired array (it's not necessary to use a list [1, 1], although you can).

Method 1

You can replace the first column as follows:

>>> a = np.zeros((2,2), dtype=np.int)
>>> a[:, 0] =  1
>>> a
array([[1, 0],
       [1, 0]])

Here a[:, 0] means “select all rows from column 0”. The value 1 is broadcast across this selected column, producing the desired array (it’s not necessary to use a list [1, 1], although you can).

Your syntax a[:][0] means “select all the rows from the array a and then select the first row”. Similarly, a[0][:] means “select the first row of a and then select this entire row again”. This is why you could replace the rows successfully, but not the columns – it’s necessary to make a selection for axis 1, not just axis 0.

Method 2

You can do something like this:

import numpy as np

a = np.zeros((2,2), dtype=np.int)
a[:,0] = np.ones((1,2), dtype=np.int)

Conclusion

It’s all About this issue. Hope all Methods helped you a lot. Comment below Your thoughts and your queries. Also, Comment below which Method worked for you? Thank You.

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