Generated Sat 22 Dec 2018 08:00:49 UTC
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: |
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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: |
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Cause: See cpydiff_core_class_mro
Workaround: See 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: |
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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: |
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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: |
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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: |
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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: |
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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: |
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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: |
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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: |
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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: |
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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: |
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