Modules

Generated Sun 18 Apr 2021 15:09:42 UTC

array

Looking for integer not implemented

Sample code:

import array

print(1 in array.array("B", b"12"))

CPy output:	uPy output:
False	Traceback (most recent call last): File "<stdin>", line 9, in <module> NotImplementedError:

Array deletion not implemented

Sample code:

import array

a = array.array("b", (1, 2, 3))
del a[1]
print(a)

CPy output:	uPy output:
array('b', [1, 3])	Traceback (most recent call last): File "<stdin>", line 10, in <module> TypeError: 'array' object doesn't support item deletion

Subscript with step != 1 is not yet implemented

Sample code:

import array

a = array.array("b", (1, 2, 3))
print(a[3:2:2])

CPy output:	uPy output:
array('b')	Traceback (most recent call last): File "<stdin>", line 10, in <module> NotImplementedError: only slices with step=1 (aka None) are supported

builtins

Second argument to next() is not implemented

Cause: MicroPython is optimised for code space.

Workaround: Instead of val = next(it, deflt) use:

try:
    val = next(it)
except StopIteration:
    val = deflt

Sample code:

print(next(iter(range(0)), 42))

CPy output:	uPy output:
42	Traceback (most recent call last): File "<stdin>", line 12, in <module> TypeError: function takes 1 positional arguments but 2 were given

deque

Deque not implemented

Workaround: Use regular lists. micropython-lib has implementation of collections.deque.

Sample code:

import collections

D = collections.deque()
print(D)

CPy output:	uPy output:
deque([])	Traceback (most recent call last): File "<stdin>", line 9, in <module> TypeError: function missing 2 required positional arguments

json

JSON module does not throw exception when object is not serialisable

Sample code:

import json

a = bytes(x for x in range(256))
try:
    z = json.dumps(a)
    x = json.loads(z)
    print("Should not get here")
except TypeError:
    print("TypeError")

CPy output:	uPy output:
TypeError	Should not get here

os

environ attribute is not implemented

Workaround: Use getenv, putenv and unsetenv

Sample code:

import os

try:
    print(os.environ.get("NEW_VARIABLE"))
    os.environ["NEW_VARIABLE"] = "VALUE"
    print(os.environ["NEW_VARIABLE"])
except AttributeError:
    print("should not get here")
    print(os.getenv("NEW_VARIABLE"))
    os.putenv("NEW_VARIABLE", "VALUE")
    print(os.getenv("NEW_VARIABLE"))

CPy output:	uPy output:
None VALUE	should not get here None VALUE

getenv returns actual value instead of cached value

Cause: The environ attribute is not implemented

Sample code:

import os

print(os.getenv("NEW_VARIABLE"))
os.putenv("NEW_VARIABLE", "VALUE")
print(os.getenv("NEW_VARIABLE"))

CPy output:	uPy output:
None None	None VALUE

getenv only allows one argument

Workaround: Test that the return value is None

Sample code:

import os

try:
    print(os.getenv("NEW_VARIABLE", "DEFAULT"))
except TypeError:
    print("should not get here")
    # this assumes NEW_VARIABLE is never an empty variable
    print(os.getenv("NEW_VARIABLE") or "DEFAULT")

CPy output:	uPy output:
DEFAULT	should not get here DEFAULT

struct

Struct pack with too few args, not checked by uPy

Sample code:

import struct

try:
    print(struct.pack("bb", 1))
    print("Should not get here")
except:
    print("struct.error")

CPy output:	uPy output:
struct.error	b'\x01\x00' Should not get here

Struct pack with too many args, not checked by uPy

Sample code:

import struct

try:
    print(struct.pack("bb", 1, 2, 3))
    print("Should not get here")
except:
    print("struct.error")

CPy output:	uPy output:
struct.error	b'\x01\x02' Should not get here

sys

Overriding sys.stdin, sys.stdout and sys.stderr not possible

Cause: They are stored in read-only memory.

Sample code:

import sys

sys.stdin = None
print(sys.stdin)

CPy output:	uPy output:
None	Traceback (most recent call last): File "<stdin>", line 9, in <module> AttributeError: 'module' object has no attribute 'stdin'