Page 350 - Computer Science V2.0 Class 11

>>> print(greet[–5], greet[–4], greet[–3], greet[–2], greet[–1])
hello

greet

Non-negative 0 1 2 3 4
indices

h e l l o

Negative -5 -4 -3 -2 -1
indices
Fig 12.1 String greet indexing

12.1.2 Strings are Immutable!

Strings in Python are immutable, i.e., a string cannot be modified. An attempt to modify a string will yield an error.
For instance, an attempt to replace the character at index 1 ('a') with 'o' in the string 'Kamal' results in an
error:
>>> name = 'Kamal'
>>> name[1] = 'o'
Traceback (most recent call last):
File "<pyshell#55>", line 1, in <module>
name[1] = 'o'
TypeError: 'str' object does not support item assignment

Strings in Python are immutable, i.e., a string cannot be modified. An attempt to modify a string will yield an error.

However, it is perfectly fine to create a new string and assign it to an existing variable. For example,
>>> name = 'Kamal'
>>> name
'Kamal'
>>> name = 'Komal'
>>> name
'Komal'
12.1.3 Invalid Indices

An index outside the valid range of indices is said to be out of range. An attempt to access a component of a string
using an index outside of the valid range of indices will result in an error. For instance, the set of valid indices for data
stored in greet ('hello') are 0, 1, 2, 3, and 4; and -5, -4, -3, -2, and -1. Thus, accessing index 7,
which is outside these ranges, will yield an error as shown below:

>>> greet[7]
Traceback (most recent call last):
File "<pyshell#7>", line 1, in <module>
greet[7]
IndexError: string index out of range

Set of valid indexes for accessing string characters includes [0, len(string)-1] and [-len(string), -1]. An attempt to
access a component of a string using an index outside of the valid range of indices will result in an error.

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