How to Add an Extra Column to a NumPy Array?

Appending an Additional Column to a NumPy Array

Adding an extra column to a NumPy array is a straightforward task that can be accomplished using the np.c_ function. This function is specifically designed for concatenating arrays along columns, making it an ideal choice for this purpose.

To append a column of zeros, simply use the following syntax:

<code class="python">np.c_[array, np.zeros((array.shape[0], 1))]</code>

For example, given the following 2D array:

<code class="python">a = np.array([
    [1, 2, 3],
    [2, 3, 4],
])</code>

To add a column of zeros, we can use:

<code class="python">b = np.c_[a, np.zeros((a.shape[0], 1))]</code>

This will result in the following array:

<code class="python">b = np.array([
    [1, 2, 3, 0],
    [2, 3, 4, 0],
])</code>

Note:

• The np.zeros() function creates a new array of zeros with the specified shape.
• The np.c_ function requires square brackets ([ ]) instead of parentheses (( )), as it uses these brackets to concatenate arrays along columns.
• This method can also be used to append multiple additional columns at once, by passing a tuple or list of arrays.
• The np.r_ function (similar to np.c_) can be used to concatenate arrays horizontally, though square brackets should be used for this function as well.

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