list和tuple的区别

元组和列表在Python中看起来都是相似的序列类型。

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.

从5.3的文档中引证的方向。元组和序列:

虽然元组可能看起来类似于列表，但它们通常用于不同的情况和不同的目的。元组是不可变的，通常包含不同的元素序列，可以通过解包(参见本节后面的内容)或索引(对于namedtuples，甚至可以通过属性访问)访问这些元素。列表是可变的，它们的元素通常是同构的，并通过遍历列表来访问。

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"))

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。

关键的区别是元组是不可变的。这意味着一旦创建了元组，就不能更改其中的值。

因此，如果您需要更改值，请使用List。

元组的好处:

性能略有改善。 元组是不可变的，可以用作字典中的键。 如果你不能改变它，其他人也不能，也就是说你不需要担心任何API函数等改变你的元组没有被要求。

只是一个快速扩展列表vs元组响应:

由于动态特性，list分配的位桶比实际需要的内存要多。这样做是为了防止在将来附加额外项时进行昂贵的重新分配操作。 另一方面，由于是静态的，轻量级元组对象不需要保留存储它们所需的额外内存。