如何仅导入模块的一部分并停止在Python中编译其他部分？

Question

I have 2 files in my project-

**file1.py**
class A():
    # Some code...

class B():
    # Calling an API to get the data

Another file is-

**file2.py**
from file1 import A
# Some code....

The problem here is that I only want to import class A, but due to python default behavior it does compile the code written inside class B as well, which is calling an API unnecessary.

How to fix it?

Answer 1

Just split out that code into separate modules, or refactor class B to not call an API on import.

Partial imports are not supported out of the box in Python; the only option the import mechanism gives you is loading the whole file only .

This means you'd have to do your own text file loading, then parse out the parts you want, then compile and execute those parts. This is fraught with problems, because you'd have to detect any dependencies yourself to make an informed decision as to what can and can not be omitted.

If you really want to go this path, you'll want to look at the ast module to produce a tree of the objects contained in a module file. I'd use the line numbers on the objects to determine what parts of the original source file to compile (converting the tree back to bytecode is harder).