list和tuple的区别

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

List是可变的，tuples是不可变的。可变和不可变之间的主要区别是当您试图追加一个项时内存的使用。

当你创建一个变量时，一些固定的内存被分配给变量。如果它是一个列表，则分配的内存比实际使用的要多。例如，如果当前内存分配是100个字节，当你想追加第101个字节时，可能会再分配100个字节(在这种情况下总共是200个字节)。

然而，如果你知道你不经常添加新元素，那么你应该使用元组。Tuples精确地分配所需的内存大小，从而节省内存，特别是当您使用大块内存时。

这是一个Python列表的例子:

my_list = [0,1,2,3,4]
top_rock_list = ["Bohemian Rhapsody","Kashmir","Sweet Emotion", "Fortunate Son"]

这是一个Python元组的例子:

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.

对于元组，“order”只是表示用于保存信息的特定“结构”。在第一个字段中找到的值可以很容易地切换到第二个字段中，因为每个字段提供跨越两个不同维度或尺度的值。它们为不同类型的问题提供答案，通常的形式是:对于给定的对象/主题，它的属性是什么?对象/主题保持不变，属性不同。

对于列表，“order”表示序列或方向性。第二个元素必须在第一个元素之后，因为它的位置是基于一个特定的和公共的比例或维度。这些元素被视为一个整体，主要是为一个典型的形式的问题提供答案，对于一个给定的属性，这些对象/主题如何比较?属性保持不变，对象/主语不同。

在流行文化和程序员中，有无数的人不符合这些差异，也有无数的人可能会用沙拉叉吃主菜。在一天结束的时候，这很好，两者通常都可以完成工作。

总结一些更精细的细节

相似之处:

Duplicates - Both tuples and lists allow for duplicates 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

区别:-根据定义，是先验的

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}

差异——用法上的后验

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"))

前面已经提到，这种差异主要是语义上的:人们期望元组和列表表示不同的信息。但这不仅仅是一个指导方针;一些库实际上根据传递的内容表现不同。以NumPy为例(复制自另一篇文章，我要求更多的例子):

>>> 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]])

关键是，虽然NumPy可能不是标准库的一部分，但它是一个主要的Python库，在NumPy中，列表和元组是完全不同的东西。

列表是可变的;元组不是。

从docs.python.org/2/tutorial/datastructures.html

元组是不可变的，通常包含的异构序列 通过解包访问的元素(参见本节后面的内容) 或者索引(在命名元组的情况下甚至通过属性)。列表 是可变的，它们的元素通常是同质的和 通过遍历列表来访问。

PEP 484——类型提示说元组元素的类型可以单独类型化;这样你就可以说Tuple[str, int, float];但是一个带有list类型类的列表只能接受一个类型参数:list [str]，这暗示了两者的区别实际上是前者是异构的，而后者本质上是同构的。

此外，标准库通常使用tuple作为这些标准函数的返回值，而C将返回结构体。