Python NumPy Examples (array, random, arange)

Use NumPy for optimized numeric operations on arrays. Call np.array.

NumPy. Python has serious limitations in numeric processing. External libraries like NumPy can improve performance—support for GPU acceleration is even possible.

With methods like np.array, we create arrays of numbers (of various types) in NumPy. Libraries like TensorFlow use NumPy. It is well-supported.

An example. To begin using NumPy, please install it from pip (a Python installer). Once installed, you can import "numpy" as "np."

Np.array: Here we create an array with np.array. A Python List is passed to the method. We then multiply the array by 2.

Python program that uses numpy import numpy as np # Create an array of 3 elements. array_one = np.array([5, 10, 15]) print(array_one) # An array can be multiplied by an int. # ... This is an array broadcasting example. array_two = array_one * 2 print(array_two) Output [ 5 10 15] [10 20 30]

Random. With NumPy we can generate an array of random values with a method call. We specify the size as an argument to random.normal.

Here: We generate a 1-dimensional array of 5 random float values. Some of the numbers are negative.

Python program that gets random array import numpy as np # Create a 1-dimensional array of 5 random values. random_values = np.random.normal(size=[1, 5]) print(random_values) Output [[ 0.49786323 0.81794554 -0.63191935 0.25130401 0.80529426]]

Arange. With NumPy we can get an array based on ranges. The arange method receives 1, 2 or 3 arguments. This works similar to the slice syntax in Python itself.

First argument: This is the starting value for the range. So with 5, our range starts at the value 5.

Second argument: The exclusive end of the range—this value is not included in the range. With a value of 6, our range does not include 6.

Third argument: The step—this is how much each element in the resulting range is incremented. This is the same way Python slices work.

Python program that uses arange import numpy as np # Get values using arange method. # ... This is an exclusive bound. values = np.arange(5) print(values) # Two arguments can be used. # ... The second argument is an exclusive bound. values = np.arange(3, 6) print(values) # A step can be used. values = np.arange(0, 5, 2) print(values) Output [0 1 2 3 4] [3 4 5] [0 2 4]

Notes, broadcasting. A powerful feature of NumPy is broadcasting. This allows you to multiply or add two arrays together, and have the elements themselves affected by their positions.

Some notes. NumPy is a powerful library. And its support in other libraries like TensorFlow make it a non-optional one (for certain use cases).
Dot Net Perls
© 2007-2020 Sam Allen. Every person is special and unique. Send bug reports to