How to Create Array in NumPy: Syntax and Examples

To create an array in numpy, use the numpy.array() function with a list or tuple as input. This function converts the input into a NumPy array, which is efficient for numerical operations.

Syntax

The basic syntax to create a NumPy array is:

• numpy.array(object, dtype=None, copy=True, order='K', subok=False, ndmin=0)

Here:

• object: A sequence like list or tuple to convert into an array.
• dtype: (Optional) Data type of the array elements.
• copy: (Optional) Whether to copy the data or not.
• order: (Optional) Memory layout order.
• ndmin: (Optional) Minimum number of dimensions for the array.

python

import numpy as np

# Basic syntax to create an array
arr = np.array([1, 2, 3])

Example

This example shows how to create a 1D and 2D NumPy array from lists and print them.

python

import numpy as np

# Create a 1D array
array_1d = np.array([10, 20, 30, 40])

# Create a 2D array
array_2d = np.array([[1, 2, 3], [4, 5, 6]])

print("1D array:")
print(array_1d)
print("\n2D array:")
print(array_2d)

Output

1D array:
[10 20 30 40]

2D array:
[[1 2 3]
 [4 5 6]]

Common Pitfalls

Common mistakes when creating arrays include:

• Passing a single number instead of a list or tuple, which creates a zero-dimensional array.
• Mixing data types in the input list, which causes NumPy to upcast to a common type.
• Forgetting to import NumPy before using array().

Example of wrong and right usage:

python

import numpy as np

# Wrong: passing a single number creates a 0D array
single_num = np.array(5)
print("0D array:", single_num)

# Right: pass a list to create 1D array
list_num = np.array([5])
print("1D array:", list_num)

Output

0D array: 5
1D array: [5]

Quick Reference

Function	Description	Example
numpy.array()	Create array from list or tuple	np.array([1, 2, 3])
numpy.zeros()	Create array filled with zeros	np.zeros((2,3))
numpy.ones()	Create array filled with ones	np.ones((3,2))
numpy.arange()	Create array with range of values	np.arange(5)
numpy.linspace()	Create array with evenly spaced values	np.linspace(0, 1, 5)

Key Takeaways

Use numpy.array() with a list or tuple to create arrays.

Arrays can be one-dimensional or multi-dimensional depending on input.

Passing a single number creates a zero-dimensional array, not a list.

NumPy automatically infers data type but you can specify it with dtype.

Always import numpy as np before creating arrays.