JavaScript API#

Backward compatibility of the API is not guaranteed at this point.

Globals#

Functions:

async loadPyodide(options)

Load the main Pyodide wasm module and initialize it.
async globalThis.loadPyodide(options)#

Load the main Pyodide wasm module and initialize it.

Arguments

  • options.args (string[]) – Command line arguments to pass to Python on startup. See Python command line interface options for more details. Default: []

  • options.fullStdLib (boolean) – Load the full Python standard library. Setting this to false excludes unvendored modules from the standard library. Default: false

  • options.homedir (string) – The home directory which Pyodide will use inside virtual file system. Default: "/home/pyodide"

  • options.indexURL (string) – The URL from which Pyodide will load the main Pyodide runtime and packages. It is recommended that you leave this unchanged, providing an incorrect value can cause broken behavior. Default: The url that Pyodide is loaded from with the file name (pyodide.js or pyodide.mjs) removed.

  • options.jsglobals (object) – The object that Pyodide will use for the js module. Default: globalThis

  • options.lockFileURL (string) – The URL from which Pyodide will load the Pyodide repodata.json lock file. You can produce custom lock files with micropip.freeze. Default: `${indexURL}/repodata.json`

  • options.stderr ((msg: string) => void) – Override the standard error output callback.

  • options.stdin (() => string) – Override the standard input callback. Should ask the user for one line of input.

  • options.stdout ((msg: string) => void) – Override the standard output callback.

Returns

Promise<PyodideInterface> – The pyodide module.

pyodide#

Attributes:

ERRNO_CODES

A map from posix error names to error codes.

FS

An alias to the Emscripten File System API.

PATH

An alias to the Emscripten Path API.

globals

An alias to the global Python namespace.

loadedPackages

The list of packages that Pyodide has loaded.

pyodide_py

An alias to the Python pyodide package.

version

The Pyodide version.

Functions:

checkInterrupt()

Throws a KeyboardInterrupt error if a KeyboardInterrupt has been requested via the interrupt buffer.

isPyProxy(jsobj)

Is the argument a PyProxy?

async loadPackage(names, options)

Load a package or a list of packages over the network.

async loadPackagesFromImports(code, options)

Inspect a Python code chunk and use pyodide.loadPackage() to install any known packages that the code chunk imports.

async mountNativeFS(path, fileSystemHandle)

Mounts FileSystemDirectoryHandle in to the target directory.

pyimport(mod_name)

Imports a module and returns it.

registerComlink(Comlink)

Tell Pyodide about Comlink.

registerJsModule(name, module)

Registers the JavaScript object module as a JavaScript module named name.

runPython(code, options)

Runs a string of Python code from JavaScript, using pyodide.code.eval_code to evaluate the code.

async runPythonAsync(code, options)

Run a Python code string with top level await using pyodide.code.eval_code_async to evaluate the code.

setInterruptBuffer(interrupt_buffer)

Sets the interrupt buffer to be interrupt_buffer.

setStderr(options)

Sets the standard error handler.

setStdin(options)

Set a stdin handler. The stdin handler is called with zero arguments whenever stdin is read and the current input buffer is exhausted. It should return one of: - null or undefined: these are interpreted as end of file. - a number - a string - an ArrayBuffer or TypedArray with BYTES_PER_ELEMENT equal to 1. If a number is returned, it is interpreted as a single character code. The number should be between 0 and 255. If a string is returned, a new line is appended if one is not present and the resulting string is turned into a Uint8Array using TextEncoder. Returning a buffer is more efficient and allows returning partial lines of text.

setStdout(options)

Sets the standard out handler.

toPy(obj, options)

Convert a JavaScript object to a Python object as best as possible.

unpackArchive(buffer, format, options)

Unpack an archive into a target directory.

unregisterJsModule(name)

Unregisters a JavaScript module with given name that has been previously registered with pyodide.registerJsModule() or register_js_module().

Classes:

PyBuffer

A class to allow access to a Python data buffers from JavaScript.

PythonError

A JavaScript error caused by a Python exception.
pyodide.ERRNO_CODES#

type: {[code: string]: number}

A map from posix error names to error codes.

pyodide.FS#

type: any

An alias to the Emscripten File System API.

This provides a wide range of POSIX-like file/device operations, including mount which can be used to extend the in-memory filesystem with features like persistence.

While all the file systems implementations are enabled, only the default MEMFS is guaranteed to work in all runtime settings. The implementations are available as members of FS.filesystems: IDBFS, NODEFS, PROXYFS, WORKERFS.

pyodide.PATH#

type: any

An alias to the Emscripten Path API.

This provides a variety of operations for working with file system paths, such as dirname, normalize, and splitPath.

pyodide.globals#

type: PyProxy

An alias to the global Python namespace.

For example, to access a variable called foo in the Python global scope, use pyodide.globals.get("foo")

pyodide.loadedPackages#

type: {[key: string]: string}

The list of packages that Pyodide has loaded. Use Object.keys(pyodide.loadedPackages) to get the list of names of loaded packages, and pyodide.loadedPackages[package_name] to access install location for a particular package_name.

pyodide.pyodide_py#

type: PyProxy

An alias to the Python pyodide package.

You can use this to call functions defined in the Pyodide Python package from JavaScript.

pyodide.version#

type: string

The Pyodide version.

The version here follows PEP440 which is different from the one in package.json, as we want to compare this with the version of Pyodide Python package without conversion.

pyodide.checkInterrupt()#

Throws a KeyboardInterrupt error if a KeyboardInterrupt has been requested via the interrupt buffer.

This can be used to enable keyboard interrupts during execution of JavaScript code, just as PyErr_CheckSignals is used to enable keyboard interrupts during execution of C code.

pyodide.isPyProxy(jsobj)#

Is the argument a PyProxy?

Arguments

  • jsobj (any) – Object to test.

Returns

boolean (typeguard for PyProxy) – Is jsobj a PyProxy?

async pyodide.loadPackage(names, options)#

Load a package or a list of packages over the network. This installs the package in the virtual filesystem. The package needs to be imported from Python before it can be used.

Arguments

  • names (string | string[] | PyProxy) – Either a single package name or URL or a list of them. URLs can be absolute or relative. The URLs must have file name <package-name>.js and there must be a file called <package-name>.data in the same directory. The argument can be a PyProxy of a list, in which case the list will be converted to JavaScript and the PyProxy will be destroyed.

  • options.checkIntegrity (boolean) – If true, check the integrity of the downloaded packages (default: true)

  • options.errorCallback ((message: string) => void) – A callback, called with error/warning messages (optional)

  • options.messageCallback ((message: string) => void) – A callback, called with progress messages (optional)

Returns

Promise<void> –

async pyodide.loadPackagesFromImports(code, options)#

Inspect a Python code chunk and use pyodide.loadPackage() to install any known packages that the code chunk imports. Uses the Python API pyodide.code.find_imports() to inspect the code.

For example, given the following code as input

import numpy as np
x = np.array([1, 2, 3])

loadPackagesFromImports() will call pyodide.loadPackage(['numpy']).

Arguments

  • code (string) – The code to inspect.

  • options.checkIntegrity (boolean) – If true, check the integrity of the downloaded packages (default: true)

  • options.errorCallback ((message: string) => void) – A callback, called with error/warning messages (optional)

  • options.messageCallback ((message: string) => void) – A callback, called with progress messages (optional)

Returns

Promise<void> –

async pyodide.mountNativeFS(path, fileSystemHandle)#

Mounts FileSystemDirectoryHandle in to the target directory.

Arguments

  • path (string) – The absolute path in the Emscripten file system to mount the native directory. If the directory does not exist, it will be created. If it does exist, it must be empty.

  • fileSystemHandle (FileSystemDirectoryHandle) – A handle returned by navigator.storage.getDirectory() or window.showDirectoryPicker().

Returns

Promise<NativeFS> –

pyodide.pyimport(mod_name)#

Imports a module and returns it.

Warning

This function has a completely different behavior than the old removed pyimport function!

pyimport is roughly equivalent to:

pyodide.runPython(`import ${pkgname}; ${pkgname}`);

except that the global namespace will not change.

Example:

let sysmodule = pyodide.pyimport("sys");
let recursionLimit = sysmodule.getrecursionlimit();
Arguments

  • mod_name (string) – The name of the module to import

Returns

PyProxy – A PyProxy for the imported module

Tell Pyodide about Comlink. Necessary to enable importing Comlink proxies into Python.

Arguments

  • Comlink (any) –

pyodide.registerJsModule(name, module)#

Registers the JavaScript object module as a JavaScript module named name. This module can then be imported from Python using the standard Python import system. If another module by the same name has already been imported, this won’t have much effect unless you also delete the imported module from sys.modules. This calls the pyodide_py API register_js_module().

Arguments

  • name (string) – Name of the JavaScript module to add

  • module (object) – JavaScript object backing the module

pyodide.runPython(code, options)#

Runs a string of Python code from JavaScript, using pyodide.code.eval_code to evaluate the code. If the last statement in the Python code is an expression (and the code doesn’t end with a semicolon), the value of the expression is returned.

Arguments

  • code (string) – Python code to evaluate

  • options.globals (PyProxy) – An optional Python dictionary to use as the globals. Defaults to pyodide.globals.

Returns

any – The result of the Python code translated to JavaScript. See the documentation for pyodide.code.eval_code for more info.

async pyodide.runPythonAsync(code, options)#

Run a Python code string with top level await using pyodide.code.eval_code_async to evaluate the code. Returns a promise which resolves when execution completes. If the last statement in the Python code is an expression (and the code doesn’t end with a semicolon), the returned promise will resolve to the value of this expression.

For example:

let result = await pyodide.runPythonAsync(`
    from js import fetch
    response = await fetch("./repodata.json")
    packages = await response.json()
    # If final statement is an expression, its value is returned to JavaScript
    len(packages.packages.object_keys())
`);
console.log(result); // 79

Python imports

Since pyodide 0.18.0, you must call loadPackagesFromImports() to import any python packages referenced via import statements in your code. This function will no longer do it for you.

Arguments

  • code (string) – Python code to evaluate

  • options.globals (PyProxy) – An optional Python dictionary to use as the globals. Defaults to pyodide.globals.

Returns

Promise<any> – The result of the Python code translated to JavaScript.

pyodide.setInterruptBuffer(interrupt_buffer)#

Sets the interrupt buffer to be interrupt_buffer. This is only useful when Pyodide is used in a webworker. The buffer should be a SharedArrayBuffer shared with the main browser thread (or another worker). In that case, signal signum may be sent by writing signum into the interrupt buffer. If signum does not satisfy 0 < signum < 65 it will be silently ignored.

You can disable interrupts by calling setInterruptBuffer(undefined).

If you wish to trigger a KeyboardInterrupt, write SIGINT (a 2), into the interrupt buffer.

By default SIGINT raises a KeyboardInterrupt and all other signals are ignored. You can install custom signal handlers with the signal module. Even signals that normally have special meaning and can’t be overridden like SIGKILL and SIGSEGV are ignored by default and can be used for any purpose you like.

Arguments
pyodide.setStderr(options)#

Sets the standard error handler. A batched handler or a raw handler can be provided (both not both). If neither is provided, we restore the default handler.

Arguments

  • options.isatty (boolean) – Should isatty(stderr) return true or false. Can only be set to true if a raw handler is provided (default false).

  • options.batched ((a: string) => void) – A batched handler is called with a string whenever a newline character is written is written or stderr is flushed. In the former case, the received line will end with a newline, in the latter case it will not. isatty(stderr) is set to false (when using a batched handler, stderr is buffered so it is impossible to make a tty with it).

  • options.raw ((a: number) => void) – A raw handler is called with the handler is called with a number for each byte of the output to stderr.

pyodide.setStdin(options)#

Set a stdin handler.

The stdin handler is called with zero arguments whenever stdin is read and the current input buffer is exhausted. It should return one of:

If a number is returned, it is interpreted as a single character code. The number should be between 0 and 255.

If a string is returned, a new line is appended if one is not present and the resulting string is turned into a Uint8Array using TextEncoder.

Returning a buffer is more efficient and allows returning partial lines of text.

Arguments

  • options.autoEOF (boolean) – Insert an EOF automatically after each string or buffer? (default true).

  • options.error (boolean) – If this is set to true, attempts to read from stdin will always set an IO error.

  • options.isatty (boolean) – Should isatty(stdin) be true or false (default false).

  • options.stdin (InFuncType) – The stdin handler.

pyodide.setStdout(options)#

Sets the standard out handler. A batched handler or a raw handler can be provided (both not both). If neither is provided, we restore the default handler.

Arguments

  • options.isatty (boolean) – Should isatty(stdout) return true or false. Can only be set to true if a raw handler is provided (default false).

  • options.batched ((a: string) => void) – A batched handler is called with a string whenever a newline character is written is written or stdout is flushed. In the former case, the received line will end with a newline, in the latter case it will not.

  • options.raw ((a: number) => void) – A raw handler is called with the handler is called with a number for each byte of the output to stdout.

pyodide.toPy(obj, options)#

Convert a JavaScript object to a Python object as best as possible.

This is similar to JsProxy.to_py but for use from JavaScript. If the object is immutable or a PyProxy, it will be returned unchanged. If the object cannot be converted into Python, it will be returned unchanged.

See JavaScript to Python for more information.

Arguments

  • obj (any) – The object to convert.

  • options.depth (number) – Optional argument to limit the depth of the conversion.

  • options.defaultConverter ((value: any, converter: (value: any) => any, cacheConversion: (input: any, output: any) => void) => any) – Optional argument to convert objects with no default conversion. See the documentation of JsProxy.to_py.

Returns

any – The object converted to Python.

pyodide.unpackArchive(buffer, format, options)#

Unpack an archive into a target directory.

Arguments

  • buffer (TypedArray | ArrayBuffer) – The archive as an ArrayBuffer or TypedArray.

  • format (string) – The format of the archive. Should be one of the formats recognized by shutil.unpack_archive. By default the options are 'bztar', 'gztar', 'tar', 'zip', and 'wheel'. Several synonyms are accepted for each format, e.g., for 'gztar' any of '.gztar', '.tar.gz', '.tgz', 'tar.gz' or 'tgz' are considered to be synonyms.

  • options.extractDir (string) – The directory to unpack the archive into. Defaults to the working directory.

pyodide.unregisterJsModule(name)#

Unregisters a JavaScript module with given name that has been previously registered with pyodide.registerJsModule() or register_js_module(). If a JavaScript module with that name does not already exist, will throw an error. Note that if the module has already been imported, this won’t have much effect unless you also delete the imported module from sys.modules. This calls the pyodide_py API unregister_js_module().

Arguments

  • name (string) – Name of the JavaScript module to remove

class pyodide.PyBuffer()#

A class to allow access to a Python data buffers from JavaScript. These are produced by PyProxy.getBuffer() and cannot be constructed directly. When you are done, release it with the release() method. See the Python Buffer Protocol documentation for more information.

To find the element x[a_1, ..., a_n], you could use the following code:

function multiIndexToIndex(pybuff, multiIndex){
   if(multindex.length !==pybuff.ndim){
      throw new Error("Wrong length index");
   }
   let idx = pybuff.offset;
   for(let i = 0; i < pybuff.ndim; i++){
      if(multiIndex[i] < 0){
         multiIndex[i] = pybuff.shape[i] - multiIndex[i];
      }
      if(multiIndex[i] < 0 || multiIndex[i] >= pybuff.shape[i]){
         throw new Error("Index out of range");
      }
      idx += multiIndex[i] * pybuff.stride[i];
   }
   return idx;
}
console.log("entry is", pybuff.data[multiIndexToIndex(pybuff, [2, 0, -1])]);

Converting between TypedArray types

The following naive code to change the type of a typed array does not work:

// Incorrectly convert a TypedArray.
// Produces a Uint16Array that points to the entire WASM memory!
let myarray = new Uint16Array(buffer.data.buffer);

Instead, if you want to convert the output TypedArray, you need to say:

// Correctly convert a TypedArray.
let myarray = new Uint16Array(
    buffer.data.buffer,
    buffer.data.byteOffset,
    buffer.data.byteLength
);
PyBuffer.c_contiguous#

type: boolean

Is it C contiguous? See memoryview.c_contiguous.

PyBuffer.data#

type: TypedArray

The actual data. A typed array of an appropriate size backed by a segment of the WASM memory.

The type argument of PyProxy.getBuffer determines which sort of TypedArray or DataView to return. By default PyProxy.getBuffer will look at the format string to determine the most appropriate option. Most often the result is a Uint8Array.

Contiguity

If the buffer is not contiguous, the data TypedArray will contain data that is not part of the buffer. Modifying this data leads to undefined behavior.

Readonly buffers

If buffer.readonly is true, you should not modify the buffer. Modifying a readonly buffer leads to undefined behavior.

PyBuffer.f_contiguous#

type: boolean

Is it Fortran contiguous? See memoryview.f_contiguous.

PyBuffer.format#

type: string

The format string for the buffer. See Format Strings and memoryview.format.

PyBuffer.itemsize#

type: number

How large is each entry (in bytes)? See memoryview.itemsize.

PyBuffer.nbytes#

type: number

The total number of bytes the buffer takes up. This is equal to buff.data.byteLength. See memoryview.nbytes.

PyBuffer.ndim#

type: number

The number of dimensions of the buffer. If ndim is 0, the buffer represents a single scalar or struct. Otherwise, it represents an array. See memoryview.ndim.

PyBuffer.offset#

type: number

The offset of the first entry of the array. For instance if our array is 3d, then you will find array[0,0,0] at pybuf.data[pybuf.offset]

PyBuffer.readonly#

type: boolean

If the data is readonly, you should not modify it. There is no way for us to enforce this, but it may cause very weird behavior. See memoryview.readonly.

PyBuffer.shape#

type: number[]

The shape of the buffer, that is how long it is in each dimension. The length will be equal to ndim. For instance, a 2x3x4 array would have shape [2, 3, 4]. See memoryview.shape.

PyBuffer.strides#

type: number[]

An array of of length ndim giving the number of elements to skip to get to a new element in each dimension. See the example definition of a multiIndexToIndex function above. See memoryview.strides.

PyBuffer.release()#

Release the buffer. This allows the memory to be reclaimed.

class pyodide.PythonError()#

A JavaScript error caused by a Python exception.

In order to reduce the risk of large memory leaks, the PythonError contains no reference to the Python exception that caused it. You can find the actual Python exception that caused this error as sys.last_value.

See type translations of errors for more information.

Avoid leaking stack Frames

If you make a PyProxy of sys.last_value, you should be especially careful to destroy() it when you are done. You may leak a large amount of memory including the local variables of all the stack frames in the traceback if you don’t. The easiest way is to only handle the exception in Python.

PythonError.type#

type: string

The name of the Python error class, e.g, RuntimeError or KeyError.

PyProxy#

A PyProxy is an object that allows idiomatic use of a Python object from JavaScript. See Proxying from Python into JavaScript.

Attributes:

length

type

Functions:

[asyncIterator]()

This translates to the Python code aiter(obj).

[iterator]()

This translates to the Python code iter(obj).

apply(thisArg, jsargs)

The apply() method calls the specified function with a given this value, and arguments provided as an array (or an array-like object).

bind(thisArg, ...jsargs)

The bind() method creates a new function that, when called, has its this keyword set to the provided value, with a given sequence of arguments preceding any provided when the new function is called.

call(thisArg, ...jsargs)

Calls the function with a given this value and arguments provided individually.

callKwargs(...jsargs)

Call the function with key word arguments.

captureThis()

Returns a PyProxy that passes this as the first argument to the Python function.

async catch(onRejected)

Calls asyncio.ensure_future() on the awaitable and executes onRejected(error) if the Future fails.

copy()

Make a new PyProxy pointing to the same Python object.

delete(key)

This translates to the Python code del obj[key].

destroy(options)

Destroy the PyProxy.

async finally(onFinally)

Calls asyncio.ensure_future() on the awaitable and executes onFinally(error) when the Future resolves.

get(key)

This translates to the Python code obj[key].

getBuffer(type)

Get a view of the buffer data which is usable from JavaScript.

has(key)

This translates to the Python code key in obj.

isAwaitable()

Check whether the PyProxy is awaitable.

isBuffer()

Check whether the PyProxy implements the Buffer Protocol.

isCallable()

Check whether the PyProxy is callable.

isIterable()

Check whether the PyProxy is iterable.

isIterator()

Check whether the PyProxy is iterable.

next(arg=undefined)

This translates to the Python code next(obj).

return(v)

Throws a GeneratorExit into the generator and if the GeneratorExit is not caught returns the argument value {done: true, value: v}.

async return(v)

Throws a GeneratorExit into the generator and if the GeneratorExit is not caught returns the argument value {done: true, value: v}.

set(key, value)

This translates to the Python code obj[key] = value.

supportsGet()

Check whether the PyProxy.get method is available on this PyProxy.

supportsHas()

Check whether the PyProxy.has method is available on this PyProxy.

supportsLength()

Check whether the PyProxy.length getter is available on this PyProxy.

supportsSet()

Check whether the PyProxy.set method is available on this PyProxy.

async then(onFulfilled, onRejected)

Calls asyncio.ensure_future() on the awaitable, executes onFulfilled(result) when the Future resolves successfully, executes onRejected(error) when the Future fails.

throw(exc)

Throws an exception into the Generator.

async throw(exc)

Throws an exception into the Generator.

toJs(options)

Converts the PyProxy into a JavaScript object as best as possible.

toString()

PyProxy.length#

type: number

PyProxy.type#

type: string

PyProxy.[asyncIterator]()#

This translates to the Python code aiter(obj). Return an async iterator associated to the proxy. See the documentation for Symbol.asyncIterator.

Present only if the proxied Python object is asynchronous iterable (i.e., has an __aiter__() method).

This will be used implicitly by for(let x of proxy){}.

Returns

AsyncIterator<any, any, any> –

PyProxy.[iterator]()#

This translates to the Python code iter(obj). Return an iterator associated to the proxy. See the documentation for Symbol.iterator

Present only if the proxied Python object is iterable (i.e., has an __iter__() method).

This will be used implicitly by for(let x of proxy){}.

Returns

Iterator<any, any, any> –

PyProxy.apply(thisArg, jsargs)#

The apply() method calls the specified function with a given this value, and arguments provided as an array (or an array-like object). Like Function.apply().

Present only if the proxied Python object is callable (i.e., has a __call__() method).

Arguments

  • thisArg (any) – The this argument. Has no effect unless the PyProxy has captureThis set. If captureThis is set, it will be passed as the first argument to the Python function.

  • jsargs (any) – The array of arguments

Returns

any – The result from the function call.

PyProxy.bind(thisArg, ...jsargs)#

The bind() method creates a new function that, when called, has its this keyword set to the provided value, with a given sequence of arguments preceding any provided when the new function is called. See Function.bind().

If the PyProxy does not have captureThis set, the this parameter will be discarded. If it does have captureThis set, thisArg will be set to the first argument of the Python function. The returned proxy and the original proxy have the same lifetime so destroying either destroys both.

Present only if the proxied Python object is callable (i.e., has a __call__() method)

Arguments

  • thisArg (any) – The value to be passed as the this parameter to the target function func when the bound function is called.

  • jsargs (any) – Extra arguments to prepend to arguments provided to the bound function when invoking func.

Returns

PyProxy –

PyProxy.call(thisArg, ...jsargs)#

Calls the function with a given this value and arguments provided individually. See Function.call().

Present only if the proxied Python object is callable (i.e., has a __call__() method).

Arguments

  • thisArg (any) – The this argument. Has no effect unless the PyProxy has captureThis set. If captureThis is set, it will be passed as the first argument to the Python function.

  • jsargs (any) – The arguments

Returns

any – The result from the function call.

PyProxy.callKwargs(...jsargs)#

Call the function with key word arguments. The last argument must be an object with the keyword arguments. Present only if the proxied Python object is callable (i.e., has a __call__() method).

Arguments

  • jsargs (any) –

Returns

any –

PyProxy.captureThis()#

Returns a PyProxy that passes this as the first argument to the Python function. The returned PyProxy has the internal captureThis property set.

It can then be used as a method on a JavaScript object. The returned proxy and the original proxy have the same lifetime so destroying either destroys both.

For example:

let obj = { a : 7 };
pyodide.runPython(`
  def f(self):
    return self.a
`);
// Without captureThis, it doesn't work to use ``f`` as a method for `obj`:
obj.f = pyodide.globals.get("f");
obj.f(); // raises "TypeError: f() missing 1 required positional argument: 'self'"
// With captureThis, it works fine:
obj.f = pyodide.globals.get("f").captureThis();
obj.f(); // returns 7
Returns

PyProxy – The resulting PyProxy. It has the same lifetime as the original PyProxy but passes this to the wrapped function.

async PyProxy.catch(onRejected)#

Calls asyncio.ensure_future() on the awaitable and executes onRejected(error) if the Future fails.

See the documentation for Promise.catch().

Present only if the proxied Python object is awaitable (i.e., has an __await__() method)

Arguments

  • onRejected ((reason: any) => any) – A handler called with the error as an argument if the awaitable fails.

Returns

Promise<any> – The resulting Promise.

PyProxy.copy()#

Make a new PyProxy pointing to the same Python object. Useful if the PyProxy is destroyed somewhere else.

Returns

PyProxy –

PyProxy.delete(key)#

This translates to the Python code del obj[key].

Present only if the proxied Python object has a __delitem__() method.

Arguments

  • key (any) – The key to delete.

PyProxy.destroy(options)#

Destroy the PyProxy. This will release the memory. Any further attempt to use the object will raise an error.

In a browser supporting FinalizationRegistry, Pyodide will automatically destroy the PyProxy when it is garbage collected, however there is no guarantee that the finalizer will be run in a timely manner so it is better to destroy the proxy explicitly.

Arguments

  • options.destroyRoundtrip (boolean) –

  • options.message (string) – The error message to print if use is attempted after destroying. Defaults to “Object has already been destroyed”.

async PyProxy.finally(onFinally)#

Calls asyncio.ensure_future() on the awaitable and executes onFinally(error) when the Future resolves.

See the documentation for Promise.finally().

Present only if the proxied Python object is awaitable (i.e., has an __await__() method).

Arguments

  • onFinally (() => void) – A handler that is called with zero arguments when the awaitable resolves.

Returns

Promise<any> – A Promise that resolves or rejects with the same result as the original Promise, but only after executing the onFinally handler.

PyProxy.get(key)#

This translates to the Python code obj[key].

Present only if the proxied Python object has a __getitem__() method.

Arguments

  • key (any) – The key to look up.

Returns

any – The corresponding value.

PyProxy.getBuffer(type)#

Get a view of the buffer data which is usable from JavaScript. No copy is ever performed.

Present only if the proxied Python object supports the Python Buffer Protocol.

We do not support suboffsets, if the buffer requires suboffsets we will throw an error. JavaScript nd array libraries can’t handle suboffsets anyways. In this case, you should use the toJs api or copy the buffer to one that doesn’t use suboffets (using e.g., numpy.ascontiguousarray()).

If the buffer stores big endian data or half floats, this function will fail without an explicit type argument. For big endian data you can use toJs. DataView has support for big endian data, so you might want to pass 'dataview' as the type argument in that case.

Arguments

  • type (string) – The type of the data field in the output. Should be one of: "i8", "u8", "u8clamped", "i16", "u16", "i32", "u32", "i32", "u32", "i64", "u64", "f32", "f64, or "dataview". This argument is optional, if absent getBuffer will try to determine the appropriate output type based on the buffer format string (see Format Strings).

Returns

PyBuffer – PyBuffer

PyProxy.has(key)#

This translates to the Python code key in obj.

Present only if the proxied Python object has a __contains__() method.

Arguments

  • key (any) – The key to check for.

Returns

boolean – Is key present?

PyProxy.isAwaitable()#

Check whether the PyProxy is awaitable. A Typescript type guard, if this function returns true Typescript considers the PyProxy to be a Promise.

Returns

boolean (typeguard for PyProxyAwaitable) –

PyProxy.isBuffer()#

Check whether the PyProxy implements the Buffer Protocol. A Typescript type guard for PyProxy.getBuffer.

Returns

boolean (typeguard for PyProxyBuffer) –

PyProxy.isCallable()#

Check whether the PyProxy is callable. A Typescript type guard, if this returns true then Typescript considers the Proxy to be callable of signature (args... : any[]) => PyProxy | number | bigint | string | boolean | undefined.

Returns

boolean (typeguard for PyProxyCallable) –

PyProxy.isIterable()#

Check whether the PyProxy is iterable. A Typescript type guard for PyProxy.[iterator].

Returns

boolean (typeguard for PyProxyIterable) –

PyProxy.isIterator()#

Check whether the PyProxy is iterable. A Typescript type guard for PyProxy.next.

Returns

boolean (typeguard for PyProxyIterator) –

PyProxy.next(arg=undefined)#

This translates to the Python code next(obj). Returns the next value of the generator. See the documentation for Generator.next() The argument will be sent to the Python generator.

This will be used implicitly by for(let x of proxy){}.

Present only if the proxied Python object is an iterator (i.e., has a send() or __next__() method).

Arguments

  • arg (any) –

Returns

IteratorResult<any, any> – An Object with two properties: done and value. When the generator yields some_value, next returns {done : false, value : some_value}. When the generator raises a StopIteration exception, next returns {done : true, value : result_value}.

PyProxy.return(v)#

Throws a GeneratorExit into the generator and if the GeneratorExit is not caught returns the argument value {done: true, value: v}. If the generator catches the GeneratorExit and returns or yields another value the next value of the generator this is returned in the normal way. If it throws some error other than GeneratorExit or StopIteration, that error is propagated. See the documentation for Generator.return().

Present only if the proxied Python object is a generator.

Arguments
Returns

IteratorResult<any, any> – An Object with two properties: done and value. When the generator yields some_value, return returns {done : false, value : some_value}. When the generator raises a StopIteration(result_value) exception, return returns {done : true, value : result_value}.

async PyProxy.return(v)#

Throws a GeneratorExit into the generator and if the GeneratorExit is not caught returns the argument value {done: true, value: v}. If the generator catches the GeneratorExit and returns or yields another value the next value of the generator this is returned in the normal way. If it throws some error other than GeneratorExit or StopAsyncIteration, that error is propagated. See the documentation for AsyncGenerator.throw()

Present only if the proxied Python object is an asynchronous generator.

Arguments
Returns

Promise<IteratorResult<any, any> > – An Object with two properties: done and value. When the generator yields some_value, return returns {done : false, value : some_value}. When the generator raises a StopAsyncIteration exception, return returns {done : true, value : result_value}.

PyProxy.set(key, value)#

This translates to the Python code obj[key] = value.

Present only if the proxied Python object has a __setitem__() method.

Arguments

  • key (any) – The key to set.

  • value (any) – The value to set it to.

PyProxy.supportsGet()#

Check whether the PyProxy.get method is available on this PyProxy. A Typescript type guard.

Returns

boolean (typeguard for PyProxyWithGet) –

PyProxy.supportsHas()#

Check whether the PyProxy.has method is available on this PyProxy. A Typescript type guard.

Returns

boolean (typeguard for PyProxyWithHas) –

PyProxy.supportsLength()#

Check whether the PyProxy.length getter is available on this PyProxy. A Typescript type guard.

Returns

boolean (typeguard for PyProxyWithLength) –

PyProxy.supportsSet()#

Check whether the PyProxy.set method is available on this PyProxy. A Typescript type guard.

Returns

boolean (typeguard for PyProxyWithSet) –

async PyProxy.then(onFulfilled, onRejected)#

Calls asyncio.ensure_future() on the awaitable, executes onFulfilled(result) when the Future resolves successfully, executes onRejected(error) when the Future fails. Will be used implicitly by await obj.

See the documentation for Promise.then().

Present only if the proxied Python object is awaitable (i.e., has an __await__() method).

Arguments

  • onFulfilled ((value: any) => any) – A handler called with the result as an argument if the awaitable succeeds.

  • onRejected ((reason: any) => any) – A handler called with the error as an argument if the awaitable fails.

Returns

Promise<any> – The resulting Promise.

PyProxy.throw(exc)#

Throws an exception into the Generator.

See the documentation for Generator.throw().

Arguments

  • exc (any) –

Returns

IteratorResult<any, any> – An Object with two properties: done and value. When the generator yields some_value, return returns {done : false, value : some_value}. When the generator raises a StopIteration(result_value) exception, return returns {done : true, value : result_value}.

async PyProxy.throw(exc)#

Throws an exception into the Generator.

See the documentation for AsyncGenerator.throw().

Arguments

  • exc (any) –

Returns

Promise<IteratorResult<any, any> > – An Object with two properties: done and value. When the generator yields some_value, return returns {done : false, value : some_value}. When the generator raises a StopIteration(result_value) exception, return returns {done : true, value : result_value}.

PyProxy.toJs(options)#

Converts the PyProxy into a JavaScript object as best as possible. By default does a deep conversion, if a shallow conversion is desired, you can use proxy.toJs({depth : 1}). See Explicit Conversion of PyProxy for more info.

Arguments

  • options.create_pyproxies (boolean) – If false, toJs will throw a ConversionError rather than producing a PyProxy.

  • options.depth (number) – How many layers deep to perform the conversion. Defaults to infinite

  • options.pyproxies (PyProxy[]) – If provided, toJs will store all PyProxies created in this list. This allows you to easily destroy all the PyProxies by iterating the list without having to recurse over the generated structure. The most common use case is to create a new empty list, pass the list as pyproxies, and then later iterate over pyproxies to destroy all of created proxies.

  • options.default_converter ((obj: PyProxy, convert: (obj: PyProxy) => any, cacheConversion: (obj: PyProxy, result: any) => void) => any) – Optional argument to convert objects with no default conversion. See the documentation of to_js().

  • options.dict_converter ((array: Iterable<[key: string, value: any] > ) => any) – A function to be called on an iterable of pairs [key, value]. Convert this iterable of pairs to the desired output. For instance, Object.fromEntries() would convert the dict to an object, Array.from() converts it to an Array of pairs, and (it) => new Map(it) converts it to a Map (which is the default behavior).

Returns

any – The JavaScript object resulting from the conversion.

PyProxy.toString()#
Returns

string –