How To Index and Slice Strings in Python?

How To Index and Slice Strings in Python?

In Python, strings are sequences of characters. Like other sequences, strings can be indexed and sliced.

Indexing:

Each character in a string has an assigned index starting from 0 for the first character.

For the string 'Python':

P(0) y(1) t(2) h(3) o(4) n(5)

To access characters by their index:

text = 'Python' print(text[0]) # Outputs: 'P' print(text[5]) # Outputs: 'n'

You can also use negative indices to count from the end:

P(-6) y(-5) t(-4) h(-3) o(-2) n(-1)

Using negative indices:

print(text[-1]) # Outputs: 'n' print(text[-6]) # Outputs: 'P'

Slicing:

Slicing allows you to obtain a substring from a string. The syntax is:

string[start:stop:step]
  • start: The beginning index of the slice (inclusive).
  • stop: The ending index of the slice (exclusive).
  • step: The interval between characters in the slice.

Examples:

text = 'Python' print(text[1:4]) # Outputs: 'yth' (from index 1 to 3) print(text[2:]) # Outputs: 'thon' (from index 2 to the end) print(text[:4]) # Outputs: 'Pyth' (from the start to index 3) print(text[::2]) # Outputs: 'Pto' (every second character) print(text[::-1]) # Outputs: 'nohtyP' (reverse the string)

If omitted, start defaults to the beginning of the string, stop defaults to the end of the string, and step defaults to 1.

Important Notes:

  1. Attempting to access an index beyond the length of a string will result in an IndexError.
  2. Slicing, on the other hand, is more forgiving. If you specify indices outside the range, Python will adjust them to fit within the bounds.
  3. Strings in Python are immutable. This means you can't change a character in a string by its index. Instead, you'd need to create a new string with the desired changes.

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