Builtin Types

Generated Mon 20 Aug 2018 07:07:17 UTC

Exception

Exception chaining not implemented

Sample code:

try:
    raise TypeError
except TypeError:
    raise ValueError
CPy output: uPy output:
Traceback (most recent call last):
  File "<stdin>", line 8, in <module>
TypeError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 10, in <module>
ValueError
/bin/sh: ../unix/micropython: No such file or directory

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
/bin/sh: ../unix/micropython: No such file or directory

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
Traceback (most recent call last):
  File "<stdin>", line 10, in <module>
IndexError: list index out of range
/bin/sh: ../unix/micropython: No such file or directory

Exception.__init__ raises TypeError if overridden and called by subclass

Sample code:

class A(Exception):
    def __init__(self):
        Exception.__init__(self)

a = A()
CPy output: uPy output:
 
/bin/sh: ../unix/micropython: No such file or directory

bytearray

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')
/bin/sh: ../unix/micropython: No such file or directory

bytes

bytes() with keywords not implemented

Workaround: Pass the encoding as a positional paramter, e.g. print(bytes('abc', 'utf-8'))

Sample code:

print(bytes('abc', encoding='utf8'))
CPy output: uPy output:
b'abc'
/bin/sh: ../unix/micropython: No such file or directory

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'
/bin/sh: ../unix/micropython: No such file or directory

float

uPy and CPython outputs formats may differ

Sample code:

print('%.1g' % -9.9)
print('%.1e' % 9.99)
print('%.1e' % 0.999)
CPy output: uPy output:
-1e+01
1.0e+01
1.0e+00
/bin/sh: ../unix/micropython: No such file or directory

int

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
/bin/sh: ../unix/micropython: No such file or directory

Incorrect error message when passing float into to_bytes

Sample code:

try:
    int('1').to_bytes(1.0)
except TypeError as e:
    print(e)
CPy output: uPy output:
integer argument expected, got float
/bin/sh: ../unix/micropython: No such file or directory

list

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]
/bin/sh: ../unix/micropython: No such file or directory

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]
/bin/sh: ../unix/micropython: No such file or directory

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]
/bin/sh: ../unix/micropython: No such file or directory

str

UnicodeDecodeError not raised when expected

Sample code:

try:
    print(repr(str(b"\xa1\x80", 'utf8')))
    print('Should not get here')
except UnicodeDecodeError:
    print('UnicodeDecodeError')
CPy output: uPy output:
UnicodeDecodeError
/bin/sh: ../unix/micropython: No such file or directory

Start/end indices such as str.endswith(s, start) not implemented

Sample code:

print('abc'.endswith('c', 1))
CPy output: uPy output:
True
/bin/sh: ../unix/micropython: No such file or directory

Attributes/subscr not implemented

Sample code:

print('{a[0]}'.format(a=[1, 2]))
CPy output: uPy output:
1
/bin/sh: ../unix/micropython: No such file or directory

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
/bin/sh: ../unix/micropython: No such file or directory

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
/bin/sh: ../unix/micropython: No such file or directory

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']
/bin/sh: ../unix/micropython: No such file or directory

Instance of a subclass of str cannot be compared for equality with an instance of a str

Sample code:

class S(str):
    pass

s = S('hello')
print(s == 'hello')
CPy output: uPy output:
True
/bin/sh: ../unix/micropython: No such file or directory

Subscript with step != 1 is not yet implemented

Sample code:

print('abcdefghi'[0:9:2])
CPy output: uPy output:
acegi
/bin/sh: ../unix/micropython: No such file or directory

tuple

Tuple load with step != 1 not implemented

Sample code:

print((1, 2, 3, 4)[0:4:2])
CPy output: uPy output:
(1, 3)
/bin/sh: ../unix/micropython: No such file or directory