有少量常量存活在内置命名空间中。它们是：
False
¶
False 值的
bool
类型。赋值
False
是非法的和引发
SyntaxError
.
True
¶
True 值的
bool
类型。赋值
True
是非法的和引发
SyntaxError
.
None
¶
唯一值对于类型
NoneType
.
None
is frequently used to represent the absence of a value, as when default arguments are not passed to a function. Assignments to
None
是非法的和引发
SyntaxError
.
NotImplemented
¶
Special value which should be returned by the binary special methods (e.g.
__eq__()
,
__lt__()
,
__add__()
,
__rsub__()
, etc.) to indicate that the operation is not implemented with respect to the other type; may be returned by the in-place binary special methods (e.g.
__imul__()
,
__iand__()
, etc.) for the same purpose. It should not be evaluated in a boolean context.
注意
当二进制 (或原位) 方法返回
NotImplemented
the interpreter will try the reflected operation on the other type (or some other fallback, depending on the operator). If all attempts return
NotImplemented
, the interpreter will raise an appropriate exception. Incorrectly returning
NotImplemented
will result in a misleading error message or the
NotImplemented
value being returned to Python code.
见 实现算术运算 范例。
注意
NotImplementedError
and
NotImplemented
不可互换，即使它们拥有相似的名称和用途。见
NotImplementedError
了解当使用它时的有关细节。
3.9 版改变：
估算
NotImplemented
in a boolean context is deprecated. While it currently evaluates as true, it will emit a
DeprecationWarning
。它将引发
TypeError
在未来 Python 版本中。
Ellipsis
¶
如同省略文字
...
。特殊值主要用于结合用户定义的容器数据类型的扩展切片句法。
注意
名称
None
,
False
,
True
and
__debug__
无法重新赋值 (赋值它们，即使作为属性名称，引发
SyntaxError
)，所以它们可以被认为是真常量。
site
模块
¶
site
module (which is imported automatically during startup, except if the
-S
command-line option is given) adds several constants to the built-in namespace. They are useful for the interactive interpreter shell and should not be used in programs.
quit
(
code=None
)
¶
exit
(
code=None
)
¶
Objects that when printed, print a message like “Use quit() or Ctrl-D (i.e. EOF) to exit”, and when called, raise
SystemExit
with the specified exit code.
copyright
¶
credits
¶
Objects that when printed or called, print the text of copyright or credits, respectively.
license
¶
Object that when printed, prints the message “Type license() to see the full license text”, and when called, displays the full license text in a pager-like fashion (one screen at a time).