Numpy

Description

Useful commands for numpy.

Import

import numpy as np

Random

np.random.randint(10) # Generates random int between 0 and 10
np.random.random(4) # Generates random array of length 4 between 0 and 1
np.random.rand(2, 3) # Generates 2 x 3 array of floats between 0 and 1

Create numpy array

Basic array:

array = np.array([1, 2, 3, 4])
# or 
array = [1, 2, 3, 4]
array = np.array(array) # >[1, 2, 3, 4]

Zero filled array:

array = np.zeros(4) # >[0, 0, 0, 0]

1D array with n numbers:

array = np.arange(4) # >[0, 1, 2, 3]

1D random array:

array = np.random.random(4) # >[0.521, 0.219, 0.972, 0.814]

1D evenly spaced array between two numbers:

array = np.linspace(0, 1, 4) # >[0, 0.333, 0.666, 1]
# np.linspace(start, stop, n)

Operations

np.copy(arr) # Copy array
np.append(arr, vals) # Appends to end of array
np.insert(arr, 3, vals) # Appends before index 3
np.concatenate((arr, arr1), axis=0) # Put arr1 at end of arr
np.split(arr, 2) # Split into two arrays
np.sort(arr)
np.reshape(3, 5) # Reshape to 3 by 5

Information

np.shape(arr)
arr.dtype # Get datatype within array
arr.size # Get size of array
np.array_equal(arr, arr1) # Compare arrays

Arithmetic Operations

np.max(arr)
np.min(arr)
np.sum(arr)
np.mean(arr) # Mean of arr
np.std(arr) # Stdev of arr
np.sqrt(arr)
np.exp(arr) # Exponent of arr
np.add(arr, arr1) 
np.subtract(arr, arr1)
np.divide(arr, arr1)
np.multiply(arr, arr1)