NumPy arange(): Create Arrays with Regularly Spaced Values

The arange() function is similar to Python's built-in range() function, but returns a NumPy ndarray rather than a list. It is widely used for generating time axes, sequence indices, and coordinate ranges. For linearly spaced arrays with a fixed number of points, see linspace().

Syntax and Parameters 🔝

numpy.arange(start, stop, step, dtype=None)

Basic arange Examples 🔝

Passing a single argument sets the upper limit stop, starting at 0 with a step of 1:

import numpy as np

print(np.arange(0)) # []
print(np.arange(5)) # [0 1 2 3 4]

assert np.array_equal(np.arange(5), np.array([0, 1, 2, 3, 4]))

Using Start, Stop and Step 🔝

Specify explicit start, stop, and step values:

print(np.arange(start=1, stop=5, step=2)) # [1 3]
print(np.arange(1, 5, 2)) # [1 3]

# Creating an empty array when start >= stop
x = np.arange(3, 3)
print(x) # []
assert x.size == 0

Negative Intervals and Steps 🔝

When counting downwards, a negative step value is required:

print(np.arange(-10, -3, 2)) # [-10  -8  -6  -4]
print(np.arange(-3, -10, -2)) # [-3 -5 -7 -9]
print(np.arange(-3, 10, 3)) # [-3  0  3  6  9]

Floating-Point Steps 🔝

Floating-point steps are supported, though accumulation rounding can occasionally produce unexpected endpoints due to precision limits:

print(np.arange(0.4, 2.8, 0.7)) # [0.4 1.1 1.8 2.5]
print(np.arange(-2.8, 2, 0.9)) # [-2.8 -1.9 -1.  -0.1  0.8  1.7]

Specifying dtype 🔝

Enforce exact integer or floating-point data types with the dtype argument:

print(np.arange(1, 5, dtype=np.int8))   # [1 2 3 4]
print(np.arange(1, 5, dtype=np.float64)) # [1. 2. 3. 4.]

my_ar = np.arange(1, 5, dtype=np.float64)
print("Array dtype:", my_ar.dtype) # float64
assert my_ar.dtype == np.float64

Practice in Google Colab 🔝

Test arange() intervals, negative steps, float sequences, and run self-verifying test suites in our interactive Google Colab companion notebook:

Interactive Practice: Colab & GitHub

Launch the notebook directly in Google Colab to run live code cells or inspect the source repository on GitHub:

View on GitHub

Continue exploring related array creation functions: array(), zeros(), ones(), full(), eye(), and linspace().

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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