Ideas: making it easier to extend Python’s syntax
You have an Excellent Idea ® to change the Python syntax and want to find a way to include your Excellent Idea ® in your Python programs. According to Python Developers Guide, this might be doable if you are willing to follow “a few steps” including:
Get a copy of the CPython’s code repository and all the required compilers for your platform.
Modify the grammar file to add rules for the new syntax.
Modify the AST generation code; this requires a knowledge of C
Compile the AST into bytecode
Recompile the modified Python interpreter
This … can be a rather daunting task. It might get a bit easier if you grab a copy of the currently unpublished book by Anthony Shaw, CPython Internals and read it from cover to cover, but it will still remain a major task. Furthermore, it would not be easy to share your work with others so that they can try it out.
However, there is a simpler way: it is possible to run code with a modified syntax using import hooks [or, in some cases as shown later, using a custom codec.]
What is an import hook
When you write something like:
Python’s import machinery has to do the following:
Try to use various tools to find the module requested
Get the source code of that module
Execute that source code, subject to some information reported in step 1.
An import hook is an additional tool that you create to do these three steps.
Once written, you add it to
sys.meta_path so that Python’s import
machinery can make use of it.
Still, writing import hooks can be rather difficult.
[page 420] …it should be emphasized that Python’s module, package and import mechanism is one of the most complicated parts of the entire language – often poorly understood by even the most seasoned Python programmers unless they’ve devoted effort to peeling back the covers.… long discussion …[page 428] Assuming that your head hasn’t completely exploded at this point, … Last, but not least, spending some time sleeping with PEP 302 and the documentation for importlib under your pillow may be advisable.
Python Cookbook, 3rd edition, by David Beazley and Brian K. Jones
ideas is designed to facilitate the creation of such import hooks, and be a repository for examples that can be used as starting points for new ideas.
Instead of figuring out how to write an import hook, using ideas you
can focus exclusively on what what might be needed to convert your proposed new
syntax into something that Python can understand – ideas will
take care of the rest, including inserting it in
Doing something like what is described in this documentation is not recommended for production code.
But it can be fun! ;-)
Try to create a different module object.
(The original entry is located in C:\Users\Andre\github\ideas\docs\source\constants.rst, line 123.)
Add these examples
I need to add some explanations and provide links to the following examples:
importing “best answer” from StackOverflow
installing module from pypi on request (David Beazley’s talk)
(The original entry is located in C:\Users\Andre\github\ideas\docs\source\excluded.rst, line 26.)