In python, the string data types are immutable. Which means a string value cannot be updated. We can verify this by trying to update a part of the string which will led us to an error.

# Can not reassign 
t= "Tutorialspoint"
print type(t)
t[0] = "M"

When we run the above program, we get the following output −

t[0] = "M"
TypeError: ''str'' object does not support item assignment

We can further verify this by checking the memory location address of the position of the letters of the string.

.
x = ''banana''

for idx in range (0,5):
    print x[idx], "=", id(x[idx])

When we run the above program we get the following output. As you can see above a and a point to same location. Also N and N also point to the same location.

b = 91909376
a = 91836864
n = 91259888
a = 91836864
n = 91259888