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pyscript.util

This module contains general-purpose utility functions that don't fit into more specific modules. These utilities handle cross-platform compatibility between Pyodide and MicroPython, feature detection, and common type conversions:

  • as_bytearray: Convert JavaScript ArrayBuffer to Python bytearray.
  • NotSupported: Placeholder for unavailable features in specific contexts.
  • is_awaitable: Detect async functions across Python implementations.

These utilities are primarily used internally by PyScript but are available for use in application code when needed.

NotSupported

Small helper that raises exceptions if you try to get/set any attribute on it.

Source code in pyscript/util.py 
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class NotSupported:
    """
    Small helper that raises exceptions if you try to get/set any attribute on
    it.
    """

    def __init__(self, name, error):
        object.__setattr__(self, "name", name)
        object.__setattr__(self, "error", error)

    def __repr__(self):
        return f"<NotSupported {self.name} [{self.error}]>"

    def __getattr__(self, attr):
        raise AttributeError(self.error)

    def __setattr__(self, attr, value):
        raise AttributeError(self.error)

    def __call__(self, *args):
        raise TypeError(self.error)

as_bytearray(buffer)

Given a JavaScript ArrayBuffer, convert it to a Python bytearray in a MicroPython friendly manner.

Source code in pyscript/util.py 
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def as_bytearray(buffer):
    """
    Given a JavaScript `ArrayBuffer`, convert it to a Python `bytearray` in a
    MicroPython friendly manner.
    """
    ui8a = js.Uint8Array.new(buffer)
    size = ui8a.length
    ba = bytearray(size)
    for i in range(size):
        ba[i] = ui8a[i]
    return ba

is_awaitable(obj)

Returns a boolean indication if the passed in obj is an awaitable function. This is interpreter agnostic.

Info

MicroPython treats awaitables as generator functions, and if the object is a closure containing an async function or a bound method we need to work carefully.

Source code in pyscript/util.py 
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def is_awaitable(obj):
    """
    Returns a boolean indication if the passed in obj is an awaitable
    function. This is interpreter agnostic.

    !!! info
        MicroPython treats awaitables as generator functions, and if
        the object is a closure containing an async function or a bound method
        we need to work carefully.
    """
    from pyscript import config

    if config["type"] == "mpy":
        # MicroPython doesn't appear to have a way to determine if a closure is
        # an async function except via the repr. This is a bit hacky.
        r = repr(obj)
        if "<closure <generator>" in r:
            return True
        # Same applies to bound methods.
        if "<bound_method" in r and "<generator>" in r:
            return True
        # In MicroPython, generator functions are awaitable.
        return inspect.isgeneratorfunction(obj)

    return inspect.iscoroutinefunction(obj)