I'm interested in loading a Python module that has its source embedded in a C extension. It should be possible to do something with Python's importlib machinery like importlib.util.spec_from_file_location so that the source code will appear if you are debugging. How would I implement an importlib.util.spec_from_string?
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2You want to embed Python code in a C extension for Python? Can you give an example of how that would be useful? I suspect this is more of a XY problem.Grismar– Grismar2020-06-10 02:58:11 +00:00Commented Jun 10, 2020 at 2:58
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It's because it's a plugin that embeds Python into another program.joeforker– joeforker2020-06-10 04:36:43 +00:00Commented Jun 10, 2020 at 4:36
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Is that "other program" also a Python program, or a C program? (or are you hoping to use the C extension / plugin in binary format?) I'm asking because you'll need Python itself to execute the Python code of course and if your other program isn't Python, that's not a trivial problem. If your other program is Python, I think there's better ways to resolve this than to embed the script into a C extension.Grismar– Grismar2020-06-10 04:57:50 +00:00Commented Jun 10, 2020 at 4:57
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The implementation of github.com/python/cpython/blob/master/Lib/zipimport.pyjoeforker– joeforker2020-06-20 22:52:13 +00:00Commented Jun 20, 2020 at 22:52
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2 Answers
Here's how to define a loader that takes the module's source from a string, and then creates and loads the module into sys.modules. It could be useful if the module's source is not in a file. If there is already a file then use https://docs.python.org/3/library/importlib.html#importing-a-source-file-directly
Although inspect.getsource(module) works for a subclass of importlib.abc.InspectLoader for which it would only be necessary to define get_source, tracebacks and pdb don't appear to be willing to display the source code until you inherit from SourceLoader.
import sys
import importlib.abc, importlib.util
class StringLoader(importlib.abc.SourceLoader):
def __init__(self, data):
self.data = data
def get_source(self, fullname):
return self.data
def get_data(self, path):
return self.data.encode("utf-8")
def get_filename(self, fullname):
return "<not a real path>/" + fullname + ".py"
module_name = "testmodule"
with open("testmodule.py", "r") as module:
loader = StringLoader(module.read())
spec = importlib.util.spec_from_loader(module_name, loader, origin="built-in")
module = importlib.util.module_from_spec(spec)
sys.modules[module_name] = module
spec.loader.exec_module(module)
Comments
As a quick fix, you can dump it in a temporary module, import it using exec and delete the temp module when you're done.
Here's a toy example:
dummy_src ="""
print("imported!")
x = 5
"""
with open("temp.py", "w") as f:
f.write(dummy_src)
exec("import temp")
print(temp.x)
Output:
imported!
5
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