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.

Without wasting your time, Let’s start This Article.

Table of Contents

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

**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).**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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