To slice or extract parts from a string in Python, you can use indexing and slicing. Here are some examples:
s = "Hello, world!"
# use indexing to extract a single character
print(s[0]) # 'H'
# use slicing to extract a substring
print(s[0:5]) # 'Hello'
# use negative indexing to count from the end of the string
print(s[-6:]) # 'world!'
# use slicing with a step to extract every other character
print(s[::2]) # 'Hlo ol!'
# use slicing with a negative step to reverse the string
print(s[::-1]) # '!dlrow ,olleH'
Note that string objects are immutable in Python, so slicing and indexing operations will always create new string objects rather than modifying the original string in place.