A Python string is a sequence, which consists of zero or more characters. The string is an immutable data structure, which means they cannot be changed. For example, if you define string str1 = "Satyamev jayate", then str1 will always remain "Satyamev jayate".  You cannot edit the value of the str1 variable. Although you can reassign str1, let's discuss this with examples:

>>> str1 = "satyamev jayate"
>>> str1
'satyamev jayate'
>>> id(str1)
47173288

In the preceding example, a "satyamev jayate" string has been assigned to an str1 variable. By using the ID function, we obtained the memory address. Now, reassign the str1 variable as shown here:

>>> str1 = "Leapx"
>>> id(str1)
44909408
>>> 

You can see that the memory address of the str1 variable has been changed. But string value at memory address 47173288 will not change. Python memory management might delete the value if it is not referred by any variable. If the value exists at memory address, then you can get the value using ctypes modules as shown here:

>>> import ctypes
>>> ctypes.cast(47173288, ctypes.py_object).value
'satyamev jayate'
>>> 

In order to find the length of the string, the len() function is used as shown in the following example:

>>> a = "hello jarvis"
>>> len(a)
12
>>> b= ""
>>> len(b)
0
>>> 

Sometimes, you may want to access a particular character(s)  at a given position in the string. The subscript operator makes this possible.