Python: Mutable vs. Immutable
Everything in Python is an object . You have to understand that Python represents all its data as objects. An object’s mutability is determined by its type. Some of these objects like lists and dictionaries are mutable , meaning you can change their content without changing their identity. Other objects like integers, floats, strings and tuples are objects that can not be changed.
Strings are Immutable
Strings are immutable in Python, which means you cannot change an existing string. The best you can do is create a new string that is a variation on the original.
Instead of producing the output "ptrings immutable", this code produces the runtime error:
Why are Python strings immutable?
Which means a string value cannot be updated . Immutability is a clean and efficient solution to concurrent access. Having immutable variables means that no matter how many times the method is called with the same variable/value, the output will always be the same. Having mutable variables means that calling the same method with the same variables may not guarantee the same output, because the variable can be mutated at any time by another method or perhaps, another thread, and that is where you start to go crazy debugging.
List is mutable
Tuple is immutable
If you want to write most efficient code, you should be the knowing difference between mutable and immutable in python. Concatenating string in loops wastes lots of memory , because strings are immutable, concatenating two strings together actually creates a third string which is the combination of the previous two. If you are iterating a lot and building a large string, you will waste a lot of memory creating and throwing away objects. Use list compression join technique.
Python handles mutable and immutable objects differently. Immutable are quicker to access than mutable objects. Also, immutable objects are fundamentally expensive to "change", because doing so involves creating a copy. Changing mutable objects is cheap.
Looking for a Python job ?
Chances are you will need to prove that you know how to work with Python. These Python Interview Questions have been designed especially to get you acquainted with the nature of questions you may encounter during your interview for the subject of Python Programming . Here are the top objective type sample Python Interview questions and their answers are given just below to them. These sample questions are framed by our experts team who trains for Python training to give you an idea of type of questions which may be asked in interview.
Go to... Python Interview Questions
- Python Interview Questions FAQ - 1
- Python Interview Questions FAQ - 2
- What is python used for?
- Is Python interpreted, or compiled, or both?
- Explain how python is interpreted
- How do I install pip on Windows?
- How do you protect Python source code?
- What are the disadvantages of the Python?
- How would you achieve web scraping in Python?
- How to Python Script executable on Unix
- What is the difference between .py and .pyc files?
- What is __init__.py used for in Python?
- What does __name__=='__main__' in Python mean?
- What is docstring in Python?
- What is the difference between runtime and compile time?
- How to use *args and **kwargs in Python
- Purpose of "/" and "//" operator in python?
- What is the purpose pass statement in python?
- Why isn't there a switch or case statement in Python?
- How does the ternary operator work in Python?
- What is the purpose of "self" in Python
- How do you debug a program in Python?
- What are literals in python?
- What is Python's parameter passing mechanism?
- What is the process of compilation and Loading in python?
- Global and Local Variables in Python
- Is there a tool to help find bugs or perform static analysis?
- What does the 'yield' keyword do in Python?
- Comparison Operators != is not equal to in Python
- What is the difference between 'is' and '==' in python
- What is the difference between = and == in Python?
- How are the functions help() and dir() different?
- What is the python keyword "with" used for?
- Is all the memory freed when Python exits?
- Explain split() methods of "re" module in Python
- Accessor and Mutator methods in Python
- How to Implement an 'enum' in Python
- Important characteristics of Python Objects
- How to determine the type of instance and inheritance in Python
- How would you implement inheritance in Python?
- How is Inheritance and Overriding methods are related?
- How can you create a copy of an object in Python?
- How to avoid having class data shared among instances in Python?
- Static class variables in Python
- Difference between @staticmethod and @classmethod in Python
- How to Get a List of Class Attributes in Python
- Does Python supports interfaces like in Java or C#?
- What is used to create Unicode string in Python?
- Difference between lists and tuples in Python?
- What are differences between List and Dictionary in Python
- Different file processing modes supported by Python
- How do you append to a file in Python?
- What are the differences between the threading and multiprocessing?
- Is there any way to kill a Thread in Python?
- What is the use of lambda in Python?
- What is map, filter and reduce in python?
- Is monkey patching considered good programming practice?