When I try to view the built-in function all() in PyCharm, I could just see "pass" in the function body. How to view the actual implementation so that I could know what exactly the built-in function is doing?

def all(*args, **kwargs): # real signature unknown"""Return True if bool(x) is True for all values x in the iterable.If the iterable is empty, return True."""pass

Assuming you’re using the usual CPython interpreter, all is a builtin function object, which just has a pointer to a compiled function statically linked into the interpreter (or libpython). Showing you the x86_64 machine code at that address probably wouldn’t be very useful to the vast majority of people.

Try running your code in PyPy instead of CPython. Many things that are builtins in CPython are plain old Python code in PyPy.¹ Of course that isn’t always an option (e.g., PyPy doesn’t support 3.7 features yet, there are a few third-party extension modules that are still way too slow to use, it’s harder to build yourself if you’re on some uncommon platform…), so let’s go back to CPython.

The actual C source for that function isn’t too hard to find online. It’s in bltinmodule.c. But, unlike the source code to the Python modules in your standard library, you probably don’t have these files around. Even if you do have them, the only way to connect the binary to the source is through debugging output emitted when you compiled CPython from that source, which you probably didn’t do. But if you’re thinking that sounds like a great idea—it is. Build CPython yourself (you may want a Py_DEBUG build), and then you can just run it in your C source debugger/IDE and it can handle all the clumsy bits.

But if that sounds more scary than helpful, even though you can read basic C code and would like to find it…

How did I know where to find that code on GitHub? Well, I know where the repo is; I know the basic organization of the source into Python, Objects, Modules, etc.; I know how module names usually map to C source file names; I know that builtins is special in a few ways…

That’s all pretty simple stuff. Couldn’t you just program all that knowledge into a script, which you could then build a PyCharm plugin out of?

You can do the first 50% or so in a quick evening hack, and such things litter the shores of GitHub. But actually doing it right requires handling a ton of special cases, parsing some ugly C code, etc. And for anyone capable of writing such a thing, it’s easier to just lldb Python than to write it.

_{1. Also, even the things that are builtins are written in a mix of Python and a Python subset called RPython, which you might find easier to understand than C—then again, it’s often even harder to find that source, and the multiple levels that all look like Python can be hard to keep straight.}