NumPy – Create array filled with all ones
Last Updated :
24 Jan, 2025
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To create an array filled with all ones, given the shape and type of array, we can use numpy.ones() method of NumPy library in Python.
import numpy as np
array = np.ones(5)
print(array)
Output:
[1. 1. 1. 1. 1.]2D Array of Ones
We can also create a 2D array (matrix) filled with ones by passing a tuple to the shape parameter.
import numpy as np
# Create a 2D array of ones (3 rows, 4 columns)
ones_array_2d = np.ones((3, 4))
print(ones_array_2d)
Output
[[1. 1. 1. 1.] [1. 1. 1. 1.] [1. 1. 1. 1.]]
Array with a Specific Data Type
We can specify the data type of the array using the dtype parameter.
import numpy as np
# Create an integer array of ones with 4 elements
ones_int_array = np.ones(4, dtype=int)
print(ones_int_array)
Output
[1 1 1 1]
Explanation:
- By specifying dtype=int, we ensure that the array is of integer type instead of the default float64.
Multi-Dimensional Array of Ones
We can also create a higher-dimensional array (3D or more) by passing a tuple representing the shape.
import numpy as np
# Create a 3D array of ones with shape (2, 3, 4)
ones_array_3d = np.ones((2, 3, 4))
print(ones_array_3d)
Output
[[[1. 1. 1. 1.] [1. 1. 1. 1.] [1. 1. 1. 1.]] [[1. 1. 1. 1.] [1. 1. 1. 1.] [1. 1. 1. 1.]]]
