Lists are mutable. whereas tuples are immutable. Accessing an offset element with index makes more sense in tuples than lists, Because the elements and their index cannot be changed.
The values of list can be changed any time but the values of tuples can't be change.
The advantages and disadvantages depends upon the use. If you have such a data which you never want to change then you should have to use tuple, otherwise list is the best option.
A direction quotation from the documentation on 5.3. Tuples and Sequences:
Though tuples may seem similar to lists, they are often used in different situations and for different purposes. Tuples are immutable, and usually contain a heterogeneous sequence of elements that are accessed via unpacking (see later in this section) or indexing (or even by attribute in the case of namedtuples). Lists are mutable, and their elements are usually homogeneous and are accessed by iterating over the list.
As people have already mentioned the differences I will write about why tuples.
Why tuples are preferred?
Allocation optimization for small tuples
To reduce memory fragmentation and speed up allocations, Python reuses old tuples. If a tuple no longer needed and has less than 20 items instead of deleting it permanently Python moves it to a free list.
A free list is divided into 20 groups, where each group represents a list of tuples of length n between 0 and 20. Each group can store up to 2 000 tuples. The first (zero) group contains only 1 element and represents an empty tuple.
>>> a = (1,2,3)
>>> id(a)
4427578104
>>> del a
>>> b = (1,2,4)
>>> id(b)
4427578104
In the example above we can see that a and b have the same id. That is because we immediately occupied a destroyed tuple which was on the free list.
Allocation optimization for lists
Since lists can be modified, Python does not use the same optimization as in tuples. However, Python lists also have a free list, but it is used only for empty objects. If an empty list is deleted or collected by GC, it can be reused later.
>>> a = []
>>> id(a)
4465566792
>>> del a
>>> b = []
>>> id(b)
4465566792
Source: https://rushter.com/blog/python-lists-and-tuples/
Why tuples are efficient than lists? -> https://stackoverflow.com/a/22140115
The most important difference is time ! When you do not want to change the data inside the list better to use tuple ! Here is the example why use tuple !
import timeit
print(timeit.timeit(stmt='[1,2,3,4,5,6,7,8,9,10]', number=1000000)) #created list
print(timeit.timeit(stmt='(1,2,3,4,5,6,7,8,9,10)', number=1000000)) # created tuple
In this example we executed both statements 1 million times
Output :
0.136621
0.013722200000000018
Any one can clearly notice the time difference.
Lists are mutable; tuples are not.
From docs.python.org/2/tutorial/datastructures.html
Tuples are immutable, and usually contain an heterogeneous sequence of elements that are accessed via unpacking (see later in this section) or indexing (or even by attribute in the case of namedtuples). Lists are mutable, and their elements are usually homogeneous and are accessed by iterating over the list.
This is an example of Python lists:
my_list = [0,1,2,3,4]
top_rock_list = ["Bohemian Rhapsody","Kashmir","Sweet Emotion", "Fortunate Son"]
This is an example of Python tuple:
my_tuple = (a,b,c,d,e)
celebrity_tuple = ("John", "Wayne", 90210, "Actor", "Male", "Dead")
Python lists and tuples are similar in that they both are ordered collections of values. Besides the shallow difference that lists are created using brackets "[ ... , ... ]" and tuples using parentheses "( ... , ... )", the core technical "hard coded in Python syntax" difference between them is that the elements of a particular tuple are immutable whereas lists are mutable (...so only tuples are hashable and can be used as dictionary/hash keys!). This gives rise to differences in how they can or can't be used (enforced a priori by syntax) and differences in how people choose to use them (encouraged as 'best practices,' a posteriori, this is what smart programers do). The main difference a posteriori in differentiating when tuples are used versus when lists are used lies in what meaning people give to the order of elements.
For tuples, 'order' signifies nothing more than just a specific 'structure' for holding information. What values are found in the first field can easily be switched into the second field as each provides values across two different dimensions or scales. They provide answers to different types of questions and are typically of the form: for a given object/subject, what are its attributes? The object/subject stays constant, the attributes differ.
For lists, 'order' signifies a sequence or a directionality. The second element MUST come after the first element because it's positioned in the 2nd place based on a particular and common scale or dimension. The elements are taken as a whole and mostly provide answers to a single question typically of the form, for a given attribute, how do these objects/subjects compare? The attribute stays constant, the object/subject differs.
There are countless examples of people in popular culture and programmers who don't conform to these differences and there are countless people who might use a salad fork for their main course. At the end of the day, it's fine and both can usually get the job done.
To summarize some of the finer details
Similarities:
Indexing, Selecting, & Slicing - Both tuples and lists index using integer values found within brackets. So, if you want the first 3 values of a given list or tuple, the syntax would be the same:
>>> my_list[0:3]
[0,1,2]
>>> my_tuple[0:3]
[a,b,c]
Comparing & Sorting - Two tuples or two lists are both compared by their first element, and if there is a tie, then by the second element, and so on. No further attention is paid to subsequent elements after earlier elements show a difference.
>>> [0,2,0,0,0,0]>[0,0,0,0,0,500]
True
>>> (0,2,0,0,0,0)>(0,0,0,0,0,500)
True
Differences: - A priori, by definition
Syntax - Lists use [], tuples use ()
Mutability - Elements in a given list are mutable, elements in a given tuple are NOT mutable.
# Lists are mutable:
>>> top_rock_list
['Bohemian Rhapsody', 'Kashmir', 'Sweet Emotion', 'Fortunate Son']
>>> top_rock_list[1]
'Kashmir'
>>> top_rock_list[1] = "Stairway to Heaven"
>>> top_rock_list
['Bohemian Rhapsody', 'Stairway to Heaven', 'Sweet Emotion', 'Fortunate Son']
# Tuples are NOT mutable:
>>> celebrity_tuple
('John', 'Wayne', 90210, 'Actor', 'Male', 'Dead')
>>> celebrity_tuple[5]
'Dead'
>>> celebrity_tuple[5]="Alive"
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment
Hashtables (Dictionaries) - As hashtables (dictionaries) require that its keys are hashable and therefore immutable, only tuples can act as dictionary keys, not lists.
#Lists CAN'T act as keys for hashtables(dictionaries)
>>> my_dict = {[a,b,c]:"some value"}
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'
#Tuples CAN act as keys for hashtables(dictionaries)
>>> my_dict = {("John","Wayne"): 90210}
>>> my_dict
{('John', 'Wayne'): 90210}
Differences - A posteriori, in usage
Homo vs. Heterogeneity of Elements - Generally list objects are homogenous and tuple objects are heterogeneous. That is, lists are used for objects/subjects of the same type (like all presidential candidates, or all songs, or all runners) whereas although it's not forced by), whereas tuples are more for heterogenous objects.
Looping vs. Structures - Although both allow for looping (for x in my_list...), it only really makes sense to do it for a list. Tuples are more appropriate for structuring and presenting information (%s %s residing in %s is an %s and presently %s % ("John","Wayne",90210, "Actor","Dead"))
Lists are intended to be homogeneous sequences, while tuples are heterogeneous data structures.
Tuples and lists are both seemingly similar sequence types in Python.
Literal syntax
We use parenthesis () to construct tuples and square brackets [ ] to get a new list. Also, we can use call of the appropriate type to get required structure — tuple or list.
someTuple = (4,6)
someList = [2,6]
Mutability
Tuples are immutable, while lists are mutable. This point is the base the for the following ones.
Memory usage
Due to mutability, you need more memory for lists and less memory for tuples.
Extending
You can add a new element to both tuples and lists with the only difference that the id of the tuple will be changed (i.e., we’ll have a new object).
Hashing
Tuples are hashable and lists are not. It means that you can use a tuple as a key in a dictionary. The list can't be used as a key in a dictionary, whereas a tuple can be used
tup = (1,2)
list_ = [1,2]
c = {tup : 1} # ok
c = {list_ : 1} # error
Semantics
This point is more about best practice. You should use tuples as heterogeneous data structures, while lists are homogenous sequences.
The PEP 484 -- Type Hints says that the types of elements of a tuple can be individually typed; so that you can say Tuple[str, int, float]; but a list, with List typing class can take only one type parameter: List[str], which hints that the difference of the 2 really is that the former is heterogeneous, whereas the latter intrinsically homogeneous.
Also, the standard library mostly uses the tuple as a return value from such standard functions where the C would return a struct.
Lists are for looping, tuples are for structures i.e. "%s %s" %tuple.
Lists are usually homogeneous, tuples are usually heterogeneous.
Lists are for variable length, tuples are for fixed length.
Difference between list and tuple
Literal
someTuple = (1,2)
someList = [1,2]
Size
a = tuple(range(1000))
b = list(range(1000))
a.__sizeof__() # 8024
b.__sizeof__() # 9088
Due to the smaller size of a tuple operation, it becomes a bit faster, but not that much to mention about until you have a huge number of elements.
Permitted operations
b = [1,2]
b[0] = 3 # [3, 2]
a = (1,2)
a[0] = 3 # Error
That also means that you can't delete an element or sort a tuple. However, you could add a new element to both list and tuple with the only difference that since the tuple is immutable, you are not really adding an element but you are creating a new tuple, so the id of will change
a = (1,2)
b = [1,2]
id(a) # 140230916716520
id(b) # 748527696
a += (3,) # (1, 2, 3)
b += [3] # [1, 2, 3]
id(a) # 140230916878160
id(b) # 748527696
Usage
As a list is mutable, it can't be used as a key in a dictionary, whereas a tuple can be used.
a = (1,2)
b = [1,2]
c = {a: 1} # OK
c = {b: 1} # Error
Just a quick extension to list vs tuple responses:
Due to dynamic nature, list allocates more bit buckets than the actual memory required. This is done to prevent costly reallocation operation in case extra items are appended in the future.
On the other hand, being static, lightweight tuple object does not reserve extra memory required to store them.
Lists are mutable and tuples are immutable. Just consider this example.
a = ["1", "2", "ra", "sa"] #list
b = ("1", "2", "ra", "sa") #tuple
Now change index values of list and tuple.
a[2] = 1000
print a #output : ['1', '2', 1000, 'sa']
b[2] = 1000
print b #output : TypeError: 'tuple' object does not support item assignment.
Hence proved the following code is invalid with tuple, because we attempted to update a tuple, which is not allowed.
It's been mentioned that the difference is largely semantic: people expect a tuple and list to represent different information. But this goes further than a guideline; some libraries actually behave differently based on what they are passed. Take NumPy for example (copied from another post where I ask for more examples):
>>> import numpy as np
>>> a = np.arange(9).reshape(3,3)
>>> a
array([[0, 1, 2],
[3, 4, 5],
[6, 7, 8]])
>>> idx = (1,1)
>>> a[idx]
4
>>> idx = [1,1]
>>> a[idx]
array([[3, 4, 5],
[3, 4, 5]])
The point is, while NumPy may not be part of the standard library, it's a major Python library, and within NumPy lists and tuples are completely different things.
The key difference is that tuples are immutable. This means that you cannot change the values in a tuple once you have created it.
So if you're going to need to change the values use a List.
Benefits to tuples:
List is mutable and tuples is immutable. The main difference between mutable and immutable is memory usage when you are trying to append an item.
When you create a variable, some fixed memory is assigned to the variable. If it is a list, more memory is assigned than actually used. E.g. if current memory assignment is 100 bytes, when you want to append the 101th byte, maybe another 100 bytes will be assigned (in total 200 bytes in this case).
However, if you know that you are not frequently add new elements, then you should use tuples. Tuples assigns exactly size of the memory needed, and hence saves memory, especially when you use large blocks of memory.
First of all, they both are the non-scalar objects (also known as a compound objects) in Python.
+ (brand new tuple will be created of course)(3,) # -> (3) instead of (3) # -> 3[3]new_array = origin_array[:][x**2 for x in range(1,7)] gives you
[1,4,9,16,25,36] (Not readable)Using list may also cause an aliasing bug (two distinct paths pointing to the same object).
If you went for a walk, you could note your coordinates at any instant in an (x,y) tuple.
If you wanted to record your journey, you could append your location every few seconds to a list.
But you couldn't do it the other way around.
As people have already answered here that tuples are immutable while lists are mutable, but there is one important aspect of using tuples which we must remember
If the tuple contains a list or a dictionary inside it, those can be changed even if the tuple itself is immutable.
For example, let's assume we have a tuple which contains a list and a dictionary as
my_tuple = (10,20,30,[40,50],{ 'a' : 10})
we can change the contents of the list as
my_tuple[3][0] = 400
my_tuple[3][1] = 500
which makes new tuple looks like
(10, 20, 30, [400, 500], {'a': 10})
we can also change the dictionary inside tuple as
my_tuple[4]['a'] = 500
which will make the overall tuple looks like
(10, 20, 30, [400, 500], {'a': 500})
This happens because list and dictionary are the objects and these objects are not changing, but the contents its pointing to.
So the tuple remains immutable without any exception
Source: Stackoverflow.com