Pythonista itself - how was it developed?

[expaand]

Just discovered this, and am blown away! I had no idea Apple would allow such a beast.

How was this developed? How did you get the entire Python interpreter and libraries to run under Swift/Objective C and on the Apple ARM? How did you implement the graphics (for plotting, etc.)? How did you implement the integration of the libraries like gui?

Thanks for a tremendous accomplishment! I can’t wait for the updates - especially adding smooth integration with the iPad Pro 12.9 inch/2018 with a soft keyboard (which currently has some issues in landscape mode).

[ellie_ff1493]

the python interpreter runs in C, so anywhere you can run C you can run python

[dgelessus]

Well-written C code is easy to compile for different architectures, so the fact that iOS devices use ARM instead of x86 processors isn't a huge problem. CPython supports some ARM platforms natively (mainly Linux), so all of the processor-specific problems have been solved already. iOS is also Unix-based and relatively similar to macOS, so even though CPython doesn't support it natively, the differences aren't huge. There are also projects like https://github.com/pybee/Python-Apple-support, which is basically a set of patches to get CPython working properly on iOS/watchOS/tvOS. (I believe this isn't exactly what Pythonista uses - @omz probably has his own custom version of CPython.)

Interacting between C and Objective-C is also very easy, since Objective-C is more or less an extension of C. This works both ways - you can easily call C code from an Objective-C method, but you can also write regular C functions in Objective-C code, which can use Objective-C features in their implementation, but can also be called from regular C code.

Many of Pythonista's custom modules (like ui, scene, console, etc.) are implemented using CPython's C API and extension interface, which allows writing Python modules in C. So in principle it's not too difficult to expose iOS Objective-C APIs to Python - you only need to write an extension module in C with some Python-exposed functions that call the appropriate Objective-C APIs. Things get more difficult of course when you also want to provide a nice Pythonic API on the Python side - that requires defining Python classes in C code and converting between Objective-C, C and Python data types where appropriate.

Another way to interact between Python and C is using the ctypes module, which is part of the standard library, and lets you use (almost) any C API from Python at runtime, without having to compile custom C code. This can also be used to interact with Objective-C APIs, because Objective-C's runtime support library provides a pure C interface to most parts of the Objective-C language. Based on this, @omz wrote Pythonista's objc_util library, which lets you interact with Objective-C APIs and objects from Python. Some of Pythonista's modules (like editor) are implemented in pure Python using objc_util instead of using CPython's extension API. (There is also a non-Pythonista-specific library called Rubicon, which has similar goals and features as Pythonista's objc_util.)

[expaand]

Thanks, that was really informative.

[miaavery99]

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