What are Immutable Strings in Python: Python’s String Behavior

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Programs use variables that stand in for the storage locations in the computer’s memory to store data. The program’s state is defined as the information in the memory regions at any given time during execution.

Immutable strings are strings you cannot change once you create them, meaning that any data cannot be changed. They are efficient to work and secure. 

mutable and immutable strings in Python

So, let’s learn about mutable and immutable strings in Python in detail.

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Mutable And Immutable Strings In Python

Python Strings come in two types: mutable and immutable strings. First, let’s discuss mutable strings.

Mutable Strings In Python

Mutable strings can have their state changed after it is created.

mutable strings in Python

A simple example of Mutable strings:

> my_list = ['lion', 'horse', 'tiger']
>>> my_list
['lion', 'horse', 'tiger']
>>> print('Address of my_list is: {}'.format(id(my_list)))
The address of my_list is: 139929780579206

The list has changed, but the memory address remains the same even if we wish to update the first value in the list and print it out. It altered the existing value. That’s what mutable means.

>> my_list[0] = 'crocodile'
>>> my_list
['crocodile', 'horse', 'tiger']
>>> print('Address of my_list is: {}'.format(id(my_list)))
The address of my_list is: 139929780579206

Let’s examine the memory locations of the list’s values now and see what happens before and after when we alter the first element’s value.

>> my_list
['crocodile', 'horse', 'tiger']
>>> id(my_list)
>>> my_list[0]
>>> id(my_list[0])
>>> my_list[0] = 'tiger'
>>> id(my_list[0])
>>> id(my_list)

A new string object is generated as strings are immutable.. Memory addresses are not identical.

My list[0] has the id 139905997706993 when the first element’s value is “crocodile.” My list[0id] ‘s becomes 139905997706897 when the value is changed to “tiger.” You’ll see that the IDs differ.

A list retains the same address even if we modify its value or change its order. The value you changed will have a different address at that location. My list still had the same id, which was 139929780579206.

Immutable Strings In Python

And now, let’s talk about immutable strings in Python:

Immutable strings are a core concept in the Python programming language, and they are strings that you cannot change once you create them. Immutability makes strings more efficient to work with and safer from security risks.

The ‘str’ data type represents immutable strings in Python. You can create strings using single or double quotes. Strings can contain any characters, including whitespace, numbers, and symbols. Strings can also span multiple lines.

Immutable strings PythonA string cannot be altered or changed in any manner once it has been produced. If you need to change a string, you must make the necessary modifications to a new string. This means that strings are immutable objects in Python, which makes them more efficient to work with than mutable objects.

Immutability also makes strings safer from security risks. Since you cannot modify lines, they are less vulnerable to malicious attacks. When working with strings containing sensitive information, such as passwords or private information, this is highly crucial.


Python provides several functions and methods for working with strings. These include procedures for finding and replacing substrings, concatenating lines, and trimming whitespace. Additionally, Python offers roles for translating strings into different data types like floating and integers.

Python also offers several string formatting techniques. These techniques allow for the creation of strings with custom formatting, including lines with dates, currency, and other formats.

In addition to the core string functions, Python has many libraries that provide additional functionality for working with strings. These libraries include regex (regular expression) functions for more advanced string manipulation and libraries for working with text files.

Immutability has the benefit of guaranteeing that a string’s value stays constant throughout a program because no other code can change it. Debugging becomes more straightforward and reduces errors. The str() method constructs a string from a supplied value and creates immutable strings.

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For instance, the following code turns the number 6 into a series: my_string = str(6). You cannot alter the string’s value once you create it. It will generate an error if you attempt to change the string. For instance, the following code will produce an error:

<p style="padding-left: 40px;">my_string = "6" my_string[0] = "7"
In this illustration, we try to alter the string's first character.
Let's look at another example of immutable strings.
>>> phrase = 'how are you today
>>> phrase
how are you today
>>>> phrase = 'what are you doing
>>> phrase
what are you doing

It’s making a new string object rather than altering the existing one. We can use the id function we previously learned to see this in greater detail. Remember to print the memory address using the id() method.

>> phrase = 'how are you today’
>>> print('Address of phrase is: {}'.format(id(phrase)))
The address of the phrase is: 139929798564765
>>> phrase = 'what are you doing'
>>> print('Address of phrase is: {}'.format(id(phrase)))
The address of the phrase is: 139929793265789

When attempting to modify a string, a new string object is generated as strings are immutable. Memory addresses are not identical.


What makes immutability crucial in Python?

Tuples cannot be changed after they are generated in Python because they are immutable. They can perform the same sequence operations as strings, which explains why.

What are Python-like immutable strings?

Python Strings are immutable, meaning they cannot be modified or changed. Although you can assign strings to variables and reassign new strings to the same variable, you cannot reassign specific characters inside a string.

Why are immutable strings beneficial?

Because a string is immutable, its value cannot be modified, as doing so would allow a hacker to alter the value being referenced and compromise the application's security. The String is secure for multithreading since it cannot be changed. Multiple threads can share a single String object.

Why do we require immutability?

Concurrent programs benefit most from immutable objects. They are immune to thread interference and inconsistent observation since they are stateless.

Do strings have a fixed state?

String objects in Java are unchangeable. Immutable refers to the inability to be altered or changed. Once a String object is formed, it cannot have its data or state modified; instead, a new String object must be constructed.

Is immutable safe for threads?

When an object is formed, its state cannot be modified; this object is said to be immutable. Because threads must be able to write to an object's instance variables for a read/write or write/write conflict, immutable objects are thread-safe by definition.

Must strings be unchangeable?

You cannot alter the string value since it is immutable. Hackers might compromise the application's security by altering the reference value if the String loses its immutability. Due to its immutability, the String is secure for multithreading.

Why should data structures be immutable?

The main advantage of immutable data structures is related to the broader advantage of avoiding mutation: it is feasible to comprehend smaller parts of code independently of the environment in which they are executed.

Do simple immutable objects exist?

Simple things are immutable objects. These objects are naturally thread-safe and don't need any synchronization. Good building blocks for other things are immutable objects.

Do immutable classes need to be synced up?

Immutable objects are straightforward, require no synchronization, and are naturally thread-safe. However, since immutable objects are useful as building blocks for other things, we must take extra care of them.

Is an immutable data class necessary?

Data classes are a practical approach to working with objects that only carry data; they have little to do with immutability. However, you may make them unchangeable by ensuring that each of their fields is unchangeable in and of itself.


Overall, immutable strings are an essential concept in Python. They are strings that you cannot change once you create them. Immutability makes strings more efficient to work with and safer from security risks.

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