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58 lines
2.3 KiB
Plaintext
Content-Type: text/x-zim-wiki
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Wiki-Format: zim 0.4
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Creation-Date: 2012-12-02T20:49:44+08:00
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====== 4. Built-in Constants ======
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Created Sunday 02 December 2012
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A small number of constants live in the built-in namespace. They are:
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===== False =====
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The false value of the bool type.
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New in version 2.3.
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===== True =====
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The true value of the bool type.
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New in version 2.3.
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===== None =====
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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.
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Changed in version 2.4: Assignments to None are illegal and raise a SyntaxError.
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===== NotImplemented =====
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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.
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===== Ellipsis =====
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Special value used in conjunction with extended slicing syntax.
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===== __debug__ =====
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This constant is true if Python was __not started with an -O option__. See also the assert statement.
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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.
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Changed in version 2.7: Assignments to __debug__ as an attribute became illegal.
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===== 4.1. Constants added by the site module =====
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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.
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===== quit([code=None]) =====
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===== exit([code=None]) =====
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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.
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==== copyright ====
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==== license ====
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==== credits ====
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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).
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»
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indexmodules |next |previous | Python » Documentation » The Python Standard Library »
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© Copyright 1990-2012, Python Software Foundation.
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The Python Software Foundation is a non-profit corporation. Please donate.
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Last updated on Dec 02, 2012. Found a bug?
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Created using Sphinx 1.0.7.
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