pocketpy/docs/quick-start/modules.md

icon	label	order
dot	Create modules	50

Modules are stored in vm->_modules and vm->_lazy_modules. They are both dict-like objects.

Lazy modules

A lazy module is a python source file. It is compiled and executed when it is imported. Use [] operator to add a lazy module.

vm->_lazy_modules["test"] = "pi = 3.14";

import test
print(test.pi)  # 3.14

Native modules

A native module is a module written in c++ or mixed c++/python. Native modules are always compiled and executed when the VM is created.

To creata a native module, use vm->new_module(...).

PyObject* mod = vm->new_module("test");
mod->attr().set("pi", VAR(3.14));

vm->bind_func<2>(mod, "add", [](VM* vm, ArgsView args){
    i64 a = CAST(i64, args[0]);
    i64 b = CAST(i64, args[1]);
    return VAR(a + b);
});

import test
print(test.pi)  # 3.14
print(test.add(1, 2))  # 3

Module resolution

When you do import a module, the VM will try to find it in the following order:

1. Search vm->_modules, if found, return it.
2. Search vm->_lazy_modules, if found, compile and execute it, then return it.
3. Search vm->_path and try to load it from file system.

Filesystem hook

You can use set_read_file_cwd to provide a custom filesystem hook, which is used for import (3rd step). The default implementation is:

set_read_file_cwd([](const Str& name){
    std::filesystem::path path(name.sv());
    bool exists = std::filesystem::exists(path);
    if(!exists) return Bytes();
    std::string cname = name.str();
    FILE* fp = fopen(cname.c_str(), "rb");
    if(!fp) return Bytes();
    fseek(fp, 0, SEEK_END);
    std::vector<char> buffer(ftell(fp));
    fseek(fp, 0, SEEK_SET);
    fread(buffer.data(), 1, buffer.size(), fp);
    fclose(fp);
    return Bytes(std::move(buffer));
});