micropython/docs/library/builtins.rst
Damien George 3c4bfd1dec py/objexcept: Support errno attribute on OSError exceptions.
This commit adds the errno attribute to exceptions, so code can retrieve
errno codes from an OSError using exc.errno.

The implementation here simply lets `errno` (and the existing `value`)
attributes work on any exception instance (they both alias args[0]).  This
is for efficiency and to keep code size down.  The pros and cons of this
are:

Pros:
- more compatible with CPython, less difference to document and learn
- OSError().errno will correctly return None, whereas the current way of
  doing it via OSError().args[0] will raise an IndexError
- it reduces code size on most bare-metal ports (because they already have
  the errno qstr)
- for Python code that uses exc.errno the generated bytecode is 2 bytes
  smaller and more efficient to execute (compared with exc.args[0]); so
  bytecode loaded to RAM saves 2 bytes RAM for each use of this attribute,
  and bytecode that is frozen saves 2 bytes flash/ROM for each use
- it's easier/shorter to type, and saves 2 bytes of space in .py files that
  use it (for each use)

Cons:
- increases code size by 4-8 bytes on minimal ports that don't already have
  the `errno` qstr
- all exceptions now have .errno and .value attributes (a cpydiff test is
  added to address this)

See also #2407.

Signed-off-by: Damien George <damien@micropython.org>
2021-04-23 22:03:46 +10:00

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Builtin functions and exceptions
================================
All builtin functions and exceptions are described here. They are also
available via ``builtins`` module.
Functions and types
-------------------
.. function:: abs()
.. function:: all()
.. function:: any()
.. function:: bin()
.. class:: bool()
.. class:: bytearray()
.. class:: bytes()
|see_cpython| `python:bytes`.
.. function:: callable()
.. function:: chr()
.. function:: classmethod()
.. function:: compile()
.. class:: complex()
.. function:: delattr(obj, name)
The argument *name* should be a string, and this function deletes the named
attribute from the object given by *obj*.
.. class:: dict()
.. function:: dir()
.. function:: divmod()
.. function:: enumerate()
.. function:: eval()
.. function:: exec()
.. function:: filter()
.. class:: float()
.. class:: frozenset()
.. function:: getattr()
.. function:: globals()
.. function:: hasattr()
.. function:: hash()
.. function:: hex()
.. function:: id()
.. function:: input()
.. class:: int()
.. classmethod:: from_bytes(bytes, byteorder)
In MicroPython, `byteorder` parameter must be positional (this is
compatible with CPython).
.. method:: to_bytes(size, byteorder)
In MicroPython, `byteorder` parameter must be positional (this is
compatible with CPython).
.. function:: isinstance()
.. function:: issubclass()
.. function:: iter()
.. function:: len()
.. class:: list()
.. function:: locals()
.. function:: map()
.. function:: max()
.. class:: memoryview()
.. function:: min()
.. function:: next()
.. class:: object()
.. function:: oct()
.. function:: open()
.. function:: ord()
.. function:: pow()
.. function:: print()
.. function:: property()
.. function:: range()
.. function:: repr()
.. function:: reversed()
.. function:: round()
.. class:: set()
.. function:: setattr()
.. class:: slice()
The *slice* builtin is the type that slice objects have.
.. function:: sorted()
.. function:: staticmethod()
.. class:: str()
.. function:: sum()
.. function:: super()
.. class:: tuple()
.. function:: type()
.. function:: zip()
Exceptions
----------
.. exception:: AssertionError
.. exception:: AttributeError
.. exception:: Exception
.. exception:: ImportError
.. exception:: IndexError
.. exception:: KeyboardInterrupt
.. exception:: KeyError
.. exception:: MemoryError
.. exception:: NameError
.. exception:: NotImplementedError
.. exception:: OSError
.. exception:: RuntimeError
.. exception:: StopIteration
.. exception:: SyntaxError
.. exception:: SystemExit
|see_cpython| `python:SystemExit`.
.. exception:: TypeError
|see_cpython| `python:TypeError`.
.. exception:: ValueError
.. exception:: ZeroDivisionError