强调方法意味着什么？

Question

我是Python语言的新手,在执行以下操作时遇到了这种情况:

help(list)

这是我遇到的:

__add__(...)
|      x.__add__(y) <==> x+y
|  
|  __contains__(...)
|      x.__contains__(y) <==> y in x
|  
|  __delitem__(...)
|      x.__delitem__(y) <==> del x[y]

关于这些,有哪些下划线？因为当你正常使用一种方法时我们并没有使用它们(据我所知),我很难理解为什么他们会花时间在文档中用下划线写出来.

Answer 1

有关全面的说明,请参阅Python样式指南.

在实践中:

the following special forms using leading or trailing
underscores are recognized (these can generally be combined with any case
convention):

- _single_leading_underscore: weak "internal use" indicator.  E.g. "from M
  import *" does not import objects whose name starts with an underscore.

- single_trailing_underscore_: used by convention to avoid conflicts with
  Python keyword, e.g.

  Tkinter.Toplevel(master, class_='ClassName')

- __double_leading_underscore: when naming a class attribute, invokes name
  mangling (inside class FooBar, __boo becomes _FooBar__boo; see below).

- __double_leading_and_trailing_underscore__: "magic" objects or
  attributes that live in user-controlled namespaces.  E.g. __init__,
  __import__ or __file__.  Never invent such names; only use them
  as documented.

Answer 2

将方法名称用下划线括起来只是分隔命名空间的一种方法。如果一个方法以下划线开头和结尾，则只是一种约定，表明该方法不适合由外部代码使用。

您发布的简介help(list)只是意味着，当您使用 Python 的语法说时e in lst，您实际上是在调用lst.__contains__(e).