Indexes for both tuples and arrays start at 0. Tuples, somewhat surprisingly, use the. An array has some metadata associated with it, like its length. A tuple does not. Tuples are essentialy structs with anonymous field names. Ok, fine. When you do this, a python object of type list is created in the memory and the variable a refers to this object by holding its location in memory.
In fact, you can actually retrieve the location of the list object in memory by inspecting a using the id function. Now if you modify the first index of the list, and check the id again, you will get the same exact value because a is still referring to the same object. Mutability is not just a python concept, it is a programming language concept that you will encounter in various programming languages. For example, assume you have some iterable object say x , and you want to append each element of x to a list.
This works alright. You keep modifying the list object in place until all the elements of x exist in the list L. Since tuples are immutable, you are basically copying the contents of the tuple T to a new tuple object at EACH iteration.
This article teaches you how to use the timeit module to measure the execution time of multiple lines of python. Now when someone tells you multiple appending to a string object is inefficient, you will understand exactly why string objects are immutable too in python.
Mutability is cool and all but one thing that can be really annoying with mutable objects is debugging. We are actually telling python that the two variables a and b should reference the same list object. Well, you are right for small snippets of code like this, but imagine if you have a big project with many references to the same mutable object. It will be very challenging to track all the changes to this object because any modification by any of those references will modify the object. Another benefit of immutability is that it allows the implementation of the language to be more memory efficient.
In CPython the most popular implementation of Python if you create immutable objects that hold the same value, python under certain conditions might bundle these different objects into one.
Remember that Strings as well as Integers, Floats, and Bools are all examples of immutable objects as well. As you can see, even though in our python program we explicitly created two different string objects, python internally bundled them into one. Well because the identity of a is exactly the same as the identity of b. Python was able to do that because the immutability of strings makes it safe to perform this bundling.
Not only that this will save us some memory by not storing the string multiple times in memory , but also every time you want to create a new object with the same value, python will just create a reference to the object that already exists in memory which is definitely more efficient. This concept is called String Interning , and this is an excellent article if you want to dive in deeper. CPython until python 3. As you can see, a has a different identity than b.
This design decision makes sense because performing interning for tuples requires making sure that all the tuple items are themselves immutable. I never leave comments on blogs but very nicely written you can tell when someone understands what they are talking about gj! Thank you for such a great article. However, I was wondering what are the advantages of tuples? Like when should we create a tuple instead of list.
Thanks Saksham! Good question. That said, if you know that your object is immutable, use tuples. Otherwise, use lists. I think this line is incorrect! Thank you so much for this explanation between Tuples and Lists.
Thanks karim ,I was confused in tuple and list but u explained very clearly with example…thanks again and keep it up. I understand the advantages of using immutable objects instead of mutable ones when using Stirngs, Floats etc. My impression is that one should always use list instead, because tuples are not more effcient than lists in terms of memory and cannot be changed. Am I missing something? In terms of memory efficiency, you are right.
But this is just an implementation detail. In other words, CPython decided not to implement interning for tuples but there is nothing in the Python programming language that stipulates that. In my opinion, I always prefer using immutable objects if I know that the objects are not going to be modified. Mutable objects sometimes lead to unexpected behavior if you are not careful. The syntaxes of each one of these data structures are different. If you have a dataset which will be assigned only once and its value should not change again, you need a tuple.
The concept of array is becoming obsolete as it is a bad memory management option and there are various shortcomings in its operation that makes it have limited usage.
If you really need to use a static array in your program, you should use tuple as it is better at memory management than an array and does the same job as a static array.
The only thing it does not do is that it does not let you change it. This property makes your data safe. But if changing the values and inserting new data in between already available data is required, then the linked list is the ideal choice as it manages memory and data perfectly and the execution time in big projects will come down significantly.
You can perform different types of operations on a list as per your requirements. Startup Resources. Kitty Gupta — May 17, Differences Between Python List, Array, and Tuple — Array — We should always start with an array as it appeared in the programming languages earlier than the rest two.
Conclusion — The concept of array is becoming obsolete as it is a bad memory management option and there are various shortcomings in its operation that makes it have limited usage. For Educators. Become an Affiliate. Terms of Service. Business Terms of Service. Careers Hiring. For Bootcamps. Blog for Business. Quality Commitment.
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