python中括号的不同含义
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different meanings of brackets in python
提问by jake wong
I am curious, what do the 3 different brackets mean in python programming? Not sure if i'm correct about this, but please correct me if i'm wrong.
我很好奇，python 编程中 3 个不同的括号是什么意思？不确定我是否正确，但如果我错了，请纠正我。
[] - # Normally used for dictionaries, list items
() - # Used to identify params
{} - # I have no idea what this does...
Or if these brackets can be used for other purposes, any advises are welcomed! Thanks!
或者如果这些括号可以用于其他目的，欢迎任何建议！谢谢！
采纳答案by Maltysen
[]: Used to define mutable data types - lists, list comprehensions and for indexing/lookup/slicing.(): Define tuples, order of operations, generator expressions, function calls and other syntax.{}: The two hash table types - dictionaries and sets.
[]：用于定义可变数据类型 - 列表、列表推导式和用于索引/查找/切片。()：定义元组、操作顺序、生成器表达式、函数调用和其他语法。{}: 两种哈希表类型 - 字典和集合。
回答by Rampant
() parentheses are used for order of operations, or order of evaluation, and are referred to as tuples. [] brackets are used for lists. List contents can be changed, unlike tuplecontent. {} are used to define a dictionary in a "list" called a literal.
() 括号用于操作顺序或求值顺序，称为元组。[] 括号用于列表。与元组内容不同，列表内容可以更改。{} 用于在称为文字的“列表”中定义字典。
回答by ttq
In addition to Maltysen's answer and for future readers: you can define the []and ()operators in a class, by defining the class methods:
除了 Maltysen 的回答以及对于未来的读者：您可以通过定义类方法在类中定义[]和()运算符：
__call__(self[, args...])for()__getitem__(self, key)for[]
An example is numpy.mgrid[...]. In this way you can define it on your custom-made objects for any purpose you like.
一个例子是numpy.mgrid[...]。通过这种方式，您可以出于您喜欢的任何目的在自定义对象上定义它。
