.. This document was generated by tools/gen-cpydiff.py
Core language
=============
Generated Wed 11 Nov 2020 02:26:58 UTC
Classes
-------
.. _cpydiff_core_class_delnotimpl:
Special method __del__ not implemented for user-defined classes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sample code::
import gc
class Foo():
def __del__(self):
print('__del__')
f = Foo()
del f
gc.collect()
+-------------+-------------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+-------------------------------------------------------------------+
| :: | :: |
| | |
| __del__ | /bin/sh: ../ports/unix/micropython: No such file or directory |
+-------------+-------------------------------------------------------------------+
.. _cpydiff_core_class_mro:
Method Resolution Order (MRO) is not compliant with CPython
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** Depth first non-exhaustive method resolution order
**Workaround:** Avoid complex class hierarchies with multiple inheritance and complex method overrides. Keep in mind that many languages don't support multiple inheritance at all.
Sample code::
class Foo:
def __str__(self):
return "Foo"
class C(tuple, Foo):
pass
t = C((1, 2, 3))
print(t)
+-------------+-------------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+-------------------------------------------------------------------+
| :: | :: |
| | |
| Foo | /bin/sh: ../ports/unix/micropython: No such file or directory |
+-------------+-------------------------------------------------------------------+
.. _cpydiff_core_class_supermultiple:
When inheriting from multiple classes super() only calls one class
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** See :ref:`cpydiff_core_class_mro`
**Workaround:** See :ref:`cpydiff_core_class_mro`
Sample code::
class A:
def __init__(self):
print("A.__init__")
class B(A):
def __init__(self):
print("B.__init__")
super().__init__()
class C(A):
def __init__(self):
print("C.__init__")
super().__init__()
class D(B,C):
def __init__(self):
print("D.__init__")
super().__init__()
D()
+----------------+-------------------------------------------------------------------+
| CPy output: | uPy output: |
+----------------+-------------------------------------------------------------------+
| :: | :: |
| | |
| D.__init__ | /bin/sh: ../ports/unix/micropython: No such file or directory |
| B.__init__ | |
| C.__init__ | |
| A.__init__ | |
+----------------+-------------------------------------------------------------------+
.. _cpydiff_core_class_superproperty:
Calling super() getter property in subclass will return a property object, not the value
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sample code::
class A:
@property
def p(self):
return {"a":10}
class AA(A):
@property
def p(self):
return super().p
a = AA()
print(a.p)
+---------------+-------------------------------------------------------------------+
| CPy output: | uPy output: |
+---------------+-------------------------------------------------------------------+
| :: | :: |
| | |
| {'a': 10} | /bin/sh: ../ports/unix/micropython: No such file or directory |
+---------------+-------------------------------------------------------------------+
Functions
---------
.. _cpydiff_core_function_argcount:
Error messages for methods may display unexpected argument counts
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** MicroPython counts "self" as an argument.
**Workaround:** Interpret error messages with the information above in mind.
Sample code::
try:
[].append()
except Exception as e:
print(e)
+---------------------------------------------------+-------------------------------------------------------------------+
| CPy output: | uPy output: |
+---------------------------------------------------+-------------------------------------------------------------------+
| :: | :: |
| | |
| append() takes exactly one argument (0 given) | /bin/sh: ../ports/unix/micropython: No such file or directory |
+---------------------------------------------------+-------------------------------------------------------------------+
.. _cpydiff_core_function_userattr:
User-defined attributes for functions are not supported
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** MicroPython is highly optimized for memory usage.
**Workaround:** Use external dictionary, e.g. ``FUNC_X[f] = 0``.
Sample code::
def f():
pass
f.x = 0
print(f.x)
+-------------+-------------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+-------------------------------------------------------------------+
| :: | :: |
| | |
| 0 | /bin/sh: ../ports/unix/micropython: No such file or directory |
+-------------+-------------------------------------------------------------------+
Generator
---------
.. _cpydiff_core_generator_noexit:
Context manager __exit__() not called in a generator which does not run to completion
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sample code::
class foo(object):
def __enter__(self):
print('Enter')
def __exit__(self, *args):
print('Exit')
def bar(x):
with foo():
while True:
x += 1
yield x
def func():
g = bar(0)
for _ in range(3):
print(next(g))
func()
+-------------+-------------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+-------------------------------------------------------------------+
| :: | :: |
| | |
| Enter | /bin/sh: ../ports/unix/micropython: No such file or directory |
| 1 | |
| 2 | |
| 3 | |
| Exit | |
+-------------+-------------------------------------------------------------------+
Runtime
-------
.. _cpydiff_core_locals:
Local variables aren't included in locals() result
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** MicroPython doesn't maintain symbolic local environment, it is optimized to an array of slots. Thus, local variables can't be accessed by a name.
Sample code::
def test():
val = 2
print(locals())
test()
+----------------+-------------------------------------------------------------------+
| CPy output: | uPy output: |
+----------------+-------------------------------------------------------------------+
| :: | :: |
| | |
| {'val': 2} | /bin/sh: ../ports/unix/micropython: No such file or directory |
+----------------+-------------------------------------------------------------------+
.. _cpydiff_core_locals_eval:
Code running in eval() function doesn't have access to local variables
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** MicroPython doesn't maintain symbolic local environment, it is optimized to an array of slots. Thus, local variables can't be accessed by a name. Effectively, ``eval(expr)`` in MicroPython is equivalent to ``eval(expr, globals(), globals())``.
Sample code::
val = 1
def test():
val = 2
print(val)
eval("print(val)")
test()
+-------------+-------------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------+-------------------------------------------------------------------+
| :: | :: |
| | |
| 2 | /bin/sh: ../ports/unix/micropython: No such file or directory |
| 2 | |
+-------------+-------------------------------------------------------------------+
import
------
.. _cpydiff_core_import_path:
__path__ attribute of a package has a different type (single string instead of list of strings) in MicroPython
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** MicroPython does't support namespace packages split across filesystem. Beyond that, MicroPython's import system is highly optimized for minimal memory usage.
**Workaround:** Details of import handling is inherently implementation dependent. Don't rely on such details in portable applications.
Sample code::
import modules
print(modules.__path__)
+------------------------------------------------------------------------------------+-------------------------------------------------------------------+
| CPy output: | uPy output: |
+------------------------------------------------------------------------------------+-------------------------------------------------------------------+
| :: | :: |
| | |
| ['/home/damien/proj/mp/kookaberry/dpgeorge-micropython/tests/cpydiff/modules'] | /bin/sh: ../ports/unix/micropython: No such file or directory |
+------------------------------------------------------------------------------------+-------------------------------------------------------------------+
.. _cpydiff_core_import_prereg:
Failed to load modules are still registered as loaded
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** To make module handling more efficient, it's not wrapped with exception handling.
**Workaround:** Test modules before production use; during development, use ``del sys.modules["name"]``, or just soft or hard reset the board.
Sample code::
import sys
try:
from modules import foo
except NameError as e:
print(e)
try:
from modules import foo
print('Should not get here')
except NameError as e:
print(e)
+-------------------------------+-------------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------------------------+-------------------------------------------------------------------+
| :: | :: |
| | |
| foo | /bin/sh: ../ports/unix/micropython: No such file or directory |
| name 'xxx' is not defined | |
| foo | |
| name 'xxx' is not defined | |
+-------------------------------+-------------------------------------------------------------------+
.. _cpydiff_core_import_split_ns_pkgs:
MicroPython does't support namespace packages split across filesystem.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
**Cause:** MicroPython's import system is highly optimized for simplicity, minimal memory usage, and minimal filesystem search overhead.
**Workaround:** Don't install modules belonging to the same namespace package in different directories. For MicroPython, it's recommended to have at most 3-component module search paths: for your current application, per-user (writable), system-wide (non-writable).
Sample code::
import sys
sys.path.append(sys.path[1] + "/modules")
sys.path.append(sys.path[1] + "/modules2")
import subpkg.foo
import subpkg.bar
print("Two modules of a split namespace package imported")
+-------------------------------------------------------+-------------------------------------------------------------------+
| CPy output: | uPy output: |
+-------------------------------------------------------+-------------------------------------------------------------------+
| :: | :: |
| | |
| Two modules of a split namespace package imported | /bin/sh: ../ports/unix/micropython: No such file or directory |
+-------------------------------------------------------+-------------------------------------------------------------------+