A small number of constants live in the built-in namespace. They are:
False
The false value of the bool
type.
New in version 2.3.
True
The true value of the bool
type.
New in version 2.3.
None
The sole value of types.NoneType
. None
is frequently used to represent the absence of a value, as when default arguments are not passed to a function.
Changed in version 2.4: Assignments to None
are illegal and raise a SyntaxError
.
NotImplemented
Special value which can be returned by the “rich comparison” special methods (__eq__()
, __lt__()
, and friends), to indicate that the comparison is not implemented with respect to the other type.
Ellipsis
Special value used in conjunction with extended slicing syntax.
__debug__
This constant is true if Python was not started with an -O
option. See also the assert
statement.
Note
The names None
and __debug__
cannot be reassigned (assignments to them, even as an attribute name, raise SyntaxError
), so they can be considered “true” constants.
Changed in version 2.7: Assignments to __debug__
as an attribute became illegal.
The 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
license
credits
Objects that when printed, print a message like “Type license() to see the full license text”, and when called, display the corresponding text in a pager-like fashion (one screen at a time).
© 2001–2017 Python Software Foundation
Licensed under the PSF License.
https://docs.python.org/2.7/library/constants.html