.. This document was generated by tools/gen-cpydiff.py
Builtin types
=============
Generated Sat 07 Oct 2023 07:35:47 UTC
Exception
---------
.. _cpydiff_types_exception_attrs:
All exceptions have readable ``value`` and ``errno`` attributes, not just ``StopIteration`` and ``OSError``.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** MicroPython is optimised to reduce code size.
**Workaround:** Only use ``value`` on ``StopIteration`` exceptions, and ``errno`` on ``OSError`` exceptions. Do not use or rely on these attributes on other exceptions.
Sample code::
e = Exception(1)
print(e.value)
print(e.errno)
+-----------------------------------------------------------------+-------------+
| CPy output: | uPy output: |
+-----------------------------------------------------------------+-------------+
| :: | :: |
| | |
| Traceback (most recent call last): | 1 |
| File "<stdin>", line 8, in <module> | 1 |
| AttributeError: 'Exception' object has no attribute 'value' | |
+-----------------------------------------------------------------+-------------+
.. _cpydiff_types_exception_chaining:
Exception chaining not implemented
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sample code::
try:
raise TypeError
except TypeError:
raise ValueError
+-------------------------------------------------------------------------+--------------------------------------------+
| CPy output: | uPy output: |
+-------------------------------------------------------------------------+--------------------------------------------+
| :: | :: |
| | |
| Traceback (most recent call last): | Traceback (most recent call last): |
| File "<stdin>", line 8, in <module> | File "<stdin>", line 10, in <module> |
| TypeError | ValueError: |
| | |
| During handling of the above exception, another exception occurred: | |
| | |
| Traceback (most recent call last): | |
| File "<stdin>", line 10, in <module> | |
| ValueError | |
+-------------------------------------------------------------------------+--------------------------------------------+
.. _cpydiff_types_exception_instancevar:
User-defined attributes for builtin exceptions are not supported
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** MicroPython is highly optimized for memory usage.
**Workaround:** Use user-defined exception subclasses.
Sample code::
e = Exception()
e.x = 0
print(e.x)
+-------------+-------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+-------------------------------------------------------------+
| :: | :: |
| | |
| 0 | Traceback (most recent call last): |
| | File "<stdin>", line 8, in <module> |
| | AttributeError: 'Exception' object has no attribute 'x' |
+-------------+-------------------------------------------------------------+
.. _cpydiff_types_exception_loops:
Exception in while loop condition may have unexpected line number
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** Condition checks are optimized to happen at the end of loop body, and that line number is reported.
Sample code::
l = ["-foo", "-bar"]
i = 0
while l[i][0] == "-":
print("iter")
i += 1
+--------------------------------------------+--------------------------------------------+
| CPy output: | uPy output: |
+--------------------------------------------+--------------------------------------------+
| :: | :: |
| | |
| iter | iter |
| iter | iter |
| Traceback (most recent call last): | Traceback (most recent call last): |
| File "<stdin>", line 10, in <module> | File "<stdin>", line 12, in <module> |
| IndexError: list index out of range | IndexError: list index out of range |
+--------------------------------------------+--------------------------------------------+
.. _cpydiff_types_exception_subclassinit:
Exception.__init__ method does not exist.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** Subclassing native classes is not fully supported in MicroPython.
**Workaround:** Call using ``super()`` instead::
class A(Exception):
def __init__(self):
super().__init__()
Sample code::
class A(Exception):
def __init__(self):
Exception.__init__(self)
a = A()
+-------------+-------------------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+-------------------------------------------------------------------------+
| | :: |
| | |
| | Traceback (most recent call last): |
| | File "<stdin>", line 18, in <module> |
| | File "<stdin>", line 15, in __init__ |
| | AttributeError: type object 'Exception' has no attribute '__init__' |
+-------------+-------------------------------------------------------------------------+
bytearray
---------
.. _cpydiff_types_bytearray_sliceassign:
Array slice assignment with unsupported RHS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sample code::
b = bytearray(4)
b[0:1] = [1, 2]
print(b)
+----------------------------------------+-------------------------------------------------------------+
| CPy output: | uPy output: |
+----------------------------------------+-------------------------------------------------------------+
| :: | :: |
| | |
| bytearray(b'\x01\x02\x00\x00\x00') | Traceback (most recent call last): |
| | File "<stdin>", line 8, in <module> |
| | NotImplementedError: array/bytes required on right side |
+----------------------------------------+-------------------------------------------------------------+
bytes
-----
.. _cpydiff_types_bytes_format:
bytes objects support .format() method
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** MicroPython strives to be a more regular implementation, so if both `str` and `bytes` support ``__mod__()`` (the % operator), it makes sense to support ``format()`` for both too. Support for ``__mod__`` can also be compiled out, which leaves only ``format()`` for bytes formatting.
**Workaround:** If you are interested in CPython compatibility, don't use ``.format()`` on bytes objects.
Sample code::
print(b"{}".format(1))
+--------------------------------------------------------------+-------------+
| CPy output: | uPy output: |
+--------------------------------------------------------------+-------------+
| :: | :: |
| | |
| Traceback (most recent call last): | b'1' |
| File "<stdin>", line 7, in <module> | |
| AttributeError: 'bytes' object has no attribute 'format' | |
+--------------------------------------------------------------+-------------+
.. _cpydiff_types_bytes_keywords:
bytes() with keywords not implemented
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Workaround:** Pass the encoding as a positional parameter, e.g. ``print(bytes('abc', 'utf-8'))``
Sample code::
print(bytes("abc", encoding="utf8"))
+-------------+----------------------------------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+----------------------------------------------------------------------------------------+
| :: | :: |
| | |
| b'abc' | Traceback (most recent call last): |
| | File "<stdin>", line 7, in <module> |
| | NotImplementedError: keyword argument(s) not implemented - use normal args instead |
+-------------+----------------------------------------------------------------------------------------+
.. _cpydiff_types_bytes_subscrstep:
Bytes subscription with step != 1 not implemented
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** MicroPython is highly optimized for memory usage.
**Workaround:** Use explicit loop for this very rare operation.
Sample code::
print(b"123"[0:3:2])
+-------------+---------------------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+---------------------------------------------------------------------------+
| :: | :: |
| | |
| b'13' | Traceback (most recent call last): |
| | File "<stdin>", line 7, in <module> |
| | NotImplementedError: only slices with step=1 (aka None) are supported |
+-------------+---------------------------------------------------------------------------+
dict
----
.. _cpydiff_types_dict_keys_set:
Dictionary keys view does not behave as a set.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** Not implemented.
**Workaround:** Explicitly convert keys to a set before using set operations.
Sample code::
print({1: 2, 3: 4}.keys() & {1})
+-------------+------------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+------------------------------------------------------------------+
| :: | :: |
| | |
| {1} | Traceback (most recent call last): |
| | File "<stdin>", line 7, in <module> |
| | TypeError: unsupported types for __and__: 'dict_view', 'set' |
+-------------+------------------------------------------------------------------+
float
-----
.. _cpydiff_types_float_implicit_conversion:
uPy allows implicit conversion of objects in maths operations while CPython does not.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Workaround:** Objects should be wrapped in ``float(obj)`` for compatibility with CPython.
Sample code::
class Test:
def __float__(self):
return 0.5
print(2.0 * Test())
+----------------------------------------------------------------------+-------------+
| CPy output: | uPy output: |
+----------------------------------------------------------------------+-------------+
| :: | :: |
| | |
| Traceback (most recent call last): | 1.0 |
| File "<stdin>", line 14, in <module> | |
| TypeError: unsupported operand type(s) for *: 'float' and 'Test' | |
+----------------------------------------------------------------------+-------------+
.. _cpydiff_types_float_rounding:
uPy and CPython outputs formats may differ
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sample code::
print("%.1g" % -9.9)
+-------------+-------------+
| CPy output: | uPy output: |
+-------------+-------------+
| :: | :: |
| | |
| -1e+01 | -10 |
+-------------+-------------+
int
---
.. _cpydiff_types_int_bit_length:
``bit_length`` method doesn't exist.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** bit_length method is not implemented.
**Workaround:** Avoid using this method on MicroPython.
Sample code::
x = 255
print("{} is {} bits long.".format(x, x.bit_length()))
+-------------------------+----------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------------------+----------------------------------------------------------------+
| :: | :: |
| | |
| 255 is 8 bits long. | Traceback (most recent call last): |
| | File "<stdin>", line 9, in <module> |
| | AttributeError: 'int' object has no attribute 'bit_length' |
+-------------------------+----------------------------------------------------------------+
.. _cpydiff_types_int_subclassconv:
No int conversion for int-derived types available
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Workaround:** Avoid subclassing builtin types unless really needed. Prefer https://en.wikipedia.org/wiki/Composition_over_inheritance .
Sample code::
class A(int):
__add__ = lambda self, other: A(int(self) + other)
a = A(42)
print(a + a)
+-------------+-------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+-------------------------------------------------------------+
| :: | :: |
| | |
| 84 | Traceback (most recent call last): |
| | File "<stdin>", line 14, in <module> |
| | File "<stdin>", line 10, in <lambda> |
| | TypeError: unsupported types for __radd__: 'int', 'int' |
+-------------+-------------------------------------------------------------+
list
----
.. _cpydiff_types_list_delete_subscrstep:
List delete with step != 1 not implemented
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Workaround:** Use explicit loop for this rare operation.
Sample code::
l = [1, 2, 3, 4]
del l[0:4:2]
print(l)
+-------------+-------------------------------------------+
| CPy output: | uPy output: |
+-------------+-------------------------------------------+
| :: | :: |
| | |
| [2, 4] | Traceback (most recent call last): |
| | File "<stdin>", line 8, in <module> |
| | NotImplementedError: |
+-------------+-------------------------------------------+
.. _cpydiff_types_list_store_noniter:
List slice-store with non-iterable on RHS is not implemented
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** RHS is restricted to be a tuple or list
**Workaround:** Use ``list(<iter>)`` on RHS to convert the iterable to a list
Sample code::
l = [10, 20]
l[0:1] = range(4)
print(l)
+----------------------+-----------------------------------------------------+
| CPy output: | uPy output: |
+----------------------+-----------------------------------------------------+
| :: | :: |
| | |
| [0, 1, 2, 3, 20] | Traceback (most recent call last): |
| | File "<stdin>", line 8, in <module> |
| | TypeError: object 'range' isn't a tuple or list |
+----------------------+-----------------------------------------------------+
.. _cpydiff_types_list_store_subscrstep:
List store with step != 1 not implemented
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Workaround:** Use explicit loop for this rare operation.
Sample code::
l = [1, 2, 3, 4]
l[0:4:2] = [5, 6]
print(l)
+------------------+-------------------------------------------+
| CPy output: | uPy output: |
+------------------+-------------------------------------------+
| :: | :: |
| | |
| [5, 2, 6, 4] | Traceback (most recent call last): |
| | File "<stdin>", line 8, in <module> |
| | NotImplementedError: |
+------------------+-------------------------------------------+
str
---
.. _cpydiff_types_str_endswith:
Start/end indices such as str.endswith(s, start) not implemented
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sample code::
print("abc".endswith("c", 1))
+-------------+--------------------------------------------+
| CPy output: | uPy output: |
+-------------+--------------------------------------------+
| :: | :: |
| | |
| True | Traceback (most recent call last): |
| | File "<stdin>", line 7, in <module> |
| | NotImplementedError: start/end indices |
+-------------+--------------------------------------------+
.. _cpydiff_types_str_formatsubscr:
Attributes/subscr not implemented
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sample code::
print("{a[0]}".format(a=[1, 2]))
+-------------+---------------------------------------------------+
| CPy output: | uPy output: |
+-------------+---------------------------------------------------+
| :: | :: |
| | |
| 1 | Traceback (most recent call last): |
| | File "<stdin>", line 7, in <module> |
| | NotImplementedError: attributes not supported |
+-------------+---------------------------------------------------+
.. _cpydiff_types_str_keywords:
str(...) with keywords not implemented
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Workaround:** Input the encoding format directly. eg ``print(bytes('abc', 'utf-8'))``
Sample code::
print(str(b"abc", encoding="utf8"))
+-------------+----------------------------------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+----------------------------------------------------------------------------------------+
| :: | :: |
| | |
| abc | Traceback (most recent call last): |
| | File "<stdin>", line 7, in <module> |
| | NotImplementedError: keyword argument(s) not implemented - use normal args instead |
+-------------+----------------------------------------------------------------------------------------+
.. _cpydiff_types_str_ljust_rjust:
str.ljust() and str.rjust() not implemented
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** MicroPython is highly optimized for memory usage. Easy workarounds available.
**Workaround:** Instead of ``s.ljust(10)`` use ``"%-10s" % s``, instead of ``s.rjust(10)`` use ``"% 10s" % s``. Alternatively, ``"{:<10}".format(s)`` or ``"{:>10}".format(s)``.
Sample code::
print("abc".ljust(10))
+-------------+-----------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+-----------------------------------------------------------+
| :: | :: |
| | |
| abc | Traceback (most recent call last): |
| | File "<stdin>", line 7, in <module> |
| | AttributeError: 'str' object has no attribute 'ljust' |
+-------------+-----------------------------------------------------------+
.. _cpydiff_types_str_rsplitnone:
None as first argument for rsplit such as str.rsplit(None, n) not implemented
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sample code::
print("a a a".rsplit(None, 1))
+------------------+-------------------------------------------+
| CPy output: | uPy output: |
+------------------+-------------------------------------------+
| :: | :: |
| | |
| ['a a', 'a'] | Traceback (most recent call last): |
| | File "<stdin>", line 7, in <module> |
| | NotImplementedError: rsplit(None,n) |
+------------------+-------------------------------------------+
.. _cpydiff_types_str_subscrstep:
Subscript with step != 1 is not yet implemented
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sample code::
print("abcdefghi"[0:9:2])
+-------------+---------------------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+---------------------------------------------------------------------------+
| :: | :: |
| | |
| acegi | Traceback (most recent call last): |
| | File "<stdin>", line 7, in <module> |
| | NotImplementedError: only slices with step=1 (aka None) are supported |
+-------------+---------------------------------------------------------------------------+
tuple
-----
.. _cpydiff_types_tuple_subscrstep:
Tuple load with step != 1 not implemented
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sample code::
print((1, 2, 3, 4)[0:4:2])
+-------------+---------------------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+---------------------------------------------------------------------------+
| :: | :: |
| | |
| (1, 3) | Traceback (most recent call last): |
| | File "<stdin>", line 7, in <module> |
| | NotImplementedError: only slices with step=1 (aka None) are supported |
+-------------+---------------------------------------------------------------------------+