Python Academy · Lesson

Indexing, Slicing, and Fancy Indexing

Access and modify array elements with advanced indexing techniques.

Basic Indexing

Access elements with zero-based integer indices. Negative indices count from the end. Multi-dimensional arrays use comma-separated indices.

import numpy as np

arr = np.array([[1,2,3],[4,5,6],[7,8,9]])
print(arr[0, 2])    # 3
print(arr[-1, -1])  # 9
print(arr[1])       # [4 5 6]

Slicing syntax start:stop:step returns a view. Applies independently on each dimension.

import numpy as np

m = np.arange(16).reshape(4,4)
print(m[1:3, 1:3])
# [[5 6]
#  [9 10]]
print(m[::2, ::2])   # every other row and column