mirror of https://github.com/pyodide/pyodide.git
111 lines
4.1 KiB
Markdown
111 lines
4.1 KiB
Markdown
# Pyodide Python compatibility
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## Python Standard library
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Most of the Python standard library is functional, except for the modules
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listed in the sections below. A large part of the CPython test suite passes except for
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tests skipped in
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[`src/tests/python_tests.yaml`](https://github.com/pyodide/pyodide/blob/main/src/tests/python_tests.yaml)
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or via [patches](https://github.com/pyodide/pyodide/tree/main/cpython/patches).
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### Optional modules
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The following stdlib modules are unvendored by default,
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in order to reduce initial download size of Python distribution.
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You can load all unvendored stdlib modules
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when initializing Pyodide with, `loadPyodide({ fullStdLib : true })`.
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However this has a significant impact on the download size.
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Instead, it is better to load individual modules as needed using
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{js:func}`pyodide.loadPackage` or {py:func}`micropip.install`.
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- ssl
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- lzma
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- sqlite3
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- test: it is an exception to the above, since it is not loaded even if `fullStdLib` is set to true.
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#### Modules with limited functionality
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- hashlib: Hash algorithms that are depending on OpenSSL are not available by default.
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See Python [hashlib documentation](https://docs.python.org/3/library/hashlib.html)
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for list of algorithms that are dependent on OpenSSL. If you need those algorithms,
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you need to call `pyodide.loadPackage('hashlib')` or `micropip.install('hashlib')`
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**before** importing hashlib.
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- decimal: The decimal module has C (\_decimal) and Python (\_pydecimal) implementations
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with the same functionality. The Python implementation is not available by default.
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If you need a Python implementation of decimal, you need to call
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`pyodide.loadPackage('pydecimal')` or `micropip.install('pydecimal')`,
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then explicitly import `_pydecimal`.
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- pydoc: Help messages for Python builtins are not available by default
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in order to reduce the initial download size. You need to call
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`pyodide.loadPackage('pydoc_data')` or `micropip.install('pydoc_data')`
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to enable them.
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- webbrowser: The original webbrowser module is not available. Instead,
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Pyodide includes some method stubs based on browser APIs:
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`webbrowser.open()`, `webbrowser.open_new()`, `webbrowser.open_new_tab()`.
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- zoneinfo: The zoneinfo package will only work if you install the timezone data using
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the tzdata package (i.e. by calling `pyodide.loadPackage("tzdata")`)
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### Synchronous HTTP requests support
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Packages for `urllib3` and `requests` are included in pyodide. In browser, these
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function _roughly_ the same as on other operating systems with some
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limitations. In node.js, they are currently untested, they will require
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at least a polyfill for synchronous XMLHttpRequest, and WebWorker.
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The first limitation is that streaming download of files only works
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in very specific circumstances, which are that pyodide has to be running
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in a web-worker, and it has to be on a cross-origin isolated website.
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If either of these conditions are not met, it will do a non-streaming
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request, i.e. download the full request body before it returns from the
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initial request call.
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Secondly, all network calls are done via the browser. This means you are
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subject to the same limitations as any JavaScript network call. This means
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you have very little or no control over certificates, timeouts, proxies and
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other network related settings. You also are constrained by browser policies
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relating to cross-origin requests, sometimes things will be blocked by CORS
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policies if the server doesn't serve them with the correct headers.
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### Removed modules
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The following modules are removed from the standard library to reduce download size and
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since they currently wouldn't work in the WebAssembly VM,
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- curses
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- dbm
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- ensurepip
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- fcntl
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- grp
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- idlelib
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- lib2to3
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- msvcrt
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- pwd
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- resource
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- syslog
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- termios
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- tkinter
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- turtle.py
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- turtledemo
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- venv
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- winreg
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- winsound
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### Included but not working modules
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The following modules can be imported, but are not functional due to the limitations of the WebAssembly VM:
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- multiprocessing
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- threading
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- sockets
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as well as any functionality that requires these.
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The following are present but cannot be imported due to a dependency on the termios package which has been removed:
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- pty
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- tty
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