All Rounder Flashcards
What is NumPy?
A library for efficient numerical computing in Python, providing N-dimensional arrays (ndarray), mathematical functions, and tools for linear algebra, Fourier transforms, and random number generation.
How to install NumPy?
Use pip install numpy.
How to import NumPy?
import numpy as np.
What are the key features of NumPy arrays?
Homogeneous data type, fixed size, and support for vectorized operations.
How to create a 1D array from a Python list?
arr = np.array([1, 2, 3]).
How to create a 2D array from a Python list?
matrix = np.array([[1, 2], [3, 4]]).
How to create an array filled with zeros?
np.zeros((3, 3)).
How to create an array filled with ones?
np.ones((2, 2)).
How to create an uninitialized array?
np.empty((3, 3)).
How to create an array with values from 0 to 10 with a step of 2?
np.arange(0, 10, 2) → [0, 2, 4, 6, 8].
How to create an array with 5 evenly spaced values between 0 and 1?
np.linspace(0, 1, 5) → [0, 0.25, 0.5, 0.75, 1].
How to create an array with random values between 0 and 1?
np.random.rand(2, 3).
What does arr.shape return?
The dimensions of the array (e.g., (3, 3) for a 3x3 array).
What does arr.ndim return?
The number of dimensions in the array (e.g., 2 for a 2D array).
What does arr.dtype return?
The data type of the array elements (e.g., float64).
What does arr.size return?
The total number of elements in the array (e.g., 9 for a 3x3 array).
How to perform element-wise addition on two arrays?
a + b (e.g., [1, 2, 3] + [4, 5, 6] → [5, 7, 9]).
How to calculate the sum of all elements in an array?
np.sum(arr).
How to calculate the mean of all elements in an array?
np.mean(arr).
How to find the maximum value along columns in a 2D array?
np.max(arr, axis=0).
What is a universal function (ufunc) in NumPy?
A function that performs element-wise operations on arrays (e.g., np.sqrt(arr)).
How to access the first element of a 1D array?
arr[0].
How to slice a 1D array to get elements from index 1 to 3?
arr[1:4].
How to filter an array using a boolean condition?
arr[arr > 2].
How to access elements of an array using a list of indices?
arr[[3, 1]].
How to reshape a 1D array into a 2D array?
arr.reshape((2, 2)).
How to flatten a 2D array into a 1D array?
arr.flatten().
How to transpose a matrix?
arr.T or np.transpose(arr).
How to join two arrays along rows?
np.concatenate([a, b], axis=0).
How to calculate the dot product of two matrices?
np.dot(a, b) or a @ b.
How to calculate the inverse of a matrix?
np.linalg.inv(a).
How to generate random integers between 0 and 10?
np.random.randint(0, 10, size=5).
How to shuffle the elements of an array?
np.random.shuffle(arr).
How to save an array to a .npy file?
np.save('array.npy', arr).
How to load an array from a .npy file?
loaded_arr = np.load('array.npy').
How to save multiple arrays to a .npz file?
np.savez('data.npz', arr1=arr1, arr2=arr2).
What is vectorization in NumPy?
Avoiding loops by using built-in functions for array operations.
How to preallocate memory for a large array?
Use np.empty() or np.zeros().
How to add 10 to every element of a 3x3 array?
arr + 10.
How to perform linear regression using NumPy?
Use np.linalg.lstsq() to compute coefficients.
