Fix ImportError: Cannot Import Name 'WordRank' From Pke_zh

Hey guys,

Encountering an ImportError can be super frustrating, especially when it involves circular imports. Let's dive into how to tackle this specific issue: ImportError: cannot import name 'WordRank' from partially initialized module 'pke_zh'. This error usually pops up when you're working with the pke_zh library in Python, particularly when there's a tangle in how your modules are importing each other. Let’s break it down and get it sorted.

Understanding the Error

First off, let's get a grip on what this error message is telling us. The key phrase here is "circular import." Think of it like two friends trying to call each other at the same time—neither can get through because they're both waiting for the other to pick up. In Python, this happens when two or more modules depend on each other, creating a loop in the import statements.

In your case, the traceback shows that you're trying to import WordRank from pke_zh. However, the pke_zh module itself is trying to import something that eventually leads back to your script (keyword.py), causing the cycle. This is why Python throws the ImportError.

Here’s a closer look at the traceback:

Traceback (most recent call last):
  File "keyword.py", line 1, in <module>
    from pke_zh import WordRank
  File "C:\Users\hcren\.conda\envs\py38\lib\site-packages\pke_zh\__init__.py", line 9, in <module>
    from pke_zh.keybert import KeyBert
  File "C:\Users\hcren\.conda\envs\py38\lib\site-packages\pke_zh\keybert.py", line 12, in <module>
    from typing import List
  File "C:\Users\hcren\.conda\envs\py38\lib\typing.py", line 21, in <module>
    import collections
  File "C:\Users\hcren\.conda\envs\py38\lib\collections\__init__.py", line 22, in <module>
    from keyword import iskeyword as _iskeyword
  File "D:\keyword.py", line 1, in <module>
    from pke_zh import WordRank
ImportError: cannot import name 'WordRank' from partially initialized module 'pke_zh' (most likely due to a circular import) (C:\Users\hcren\.conda\envs\py38\lib\site-packages\pke_zh\__init__.py)

Notice how the traceback loops back to keyword.py? That’s the circular import in action.

Common Causes and Solutions

1. Circular Dependencies

The Problem: Circular dependencies are the most frequent culprit. This happens when two or more modules import each other, creating a loop. For instance, module A imports module B, and module B imports module A. When Python tries to import one of them, it gets stuck in a loop.

The Solution: The best way to tackle this is to refactor your code to break the circular dependency. Here’s how you can do it:

• Restructure Your Code: Think about how your modules are organized. Can you move some of the code to a common module that neither A nor B depends on directly? This shared module can then be imported by both.

• Delay Imports: Sometimes, you don't need to import a module at the very top of your file. You can delay the import until you actually need it within a function or method. This can help break the cycle.

  # Instead of:
  # from module_b import SomeClass
  
  def my_function():
      from module_b import SomeClass  # Delayed import
      # Use SomeClass here
  

• Use Import Inside Functions: If a class or function in module A uses a class or function from module B only in a specific method, import module B inside that method. This defers the import and can prevent circular dependencies.

  class ModuleA:
      def my_method(self):
          from module_b import some_function  # Import inside the method
          return some_function()
  

2. Filename Conflicts

The Problem: Another common issue is naming your script the same as a library you're trying to import. In your case, if you have a file named pke_zh.py in the same directory as your script, Python might try to import your file instead of the installed library.

The Solution:

• Rename Your Script: Simply rename your script to something different from the library name. For example, change keyword.py to keywords_extraction.py.

3. Installation Issues

The Problem: Sometimes, the library might not be installed correctly, or there could be conflicting versions of dependencies.

The Solution:

• Reinstall the Library: Try uninstalling and then reinstalling pke_zh using pip.

  pip uninstall pke_zh
  pip install pke_zh
  

• Check Dependencies: Ensure that all the dependencies of pke_zh are installed and compatible. You can check the pke_zh documentation or its setup.py file for a list of dependencies.

• Use a Virtual Environment: Using a virtual environment isolates your project's dependencies from other projects, preventing conflicts. If you’re not already using one, create a virtual environment:

  python -m venv venv
  source venv/bin/activate  # On Linux/macOS
  .\venv\Scripts\activate  # On Windows
  pip install pke_zh
  

4. Incorrect Path

The Problem: Python might not be able to find the pke_zh module if it's not in the Python path.

The Solution:

• Check PYTHONPATH: Ensure that the directory where pke_zh is installed is included in your PYTHONPATH environment variable. However, manually setting PYTHONPATH is generally discouraged. Using virtual environments is a cleaner approach.

5. File Structure

The Problem: A messy project structure can sometimes lead to import issues. If your files are scattered and imports are not well-organized, circular dependencies can sneak in.

The Solution:

• Organize Your Project: Adopt a clear and consistent file structure. Group related files into directories and use relative imports to keep things tidy.

  my_project/
  ├── main.py
  ├── module_a.py
  ├── module_b.py
  └── utils/
      └── helper.py
  

  Use relative imports within the modules:

  # In module_a.py
  from . import module_b  # Relative import
  

Applying Solutions to Your Case

Given your traceback, the most likely issue is a circular import or a filename conflict. Here’s a step-by-step approach to troubleshoot:

1. Rename Your Script: First, rename keyword.py to something like keywords_extraction.py. This eliminates the possibility of a filename conflict.
2. Examine Imports: Carefully review the import statements in your script and in the pke_zh library files (if you can access them). Look for any circular dependencies.
3. Restructure Imports: If you find a circular dependency, try delaying imports or moving them inside functions.
4. Use Virtual Environment: Make sure you are working in a virtual environment to avoid conflicts with other packages.
5. Reinstall pke_zh: If the issue persists, try reinstalling the library as shown above.

Example: Restructuring Imports

Let’s say you have two modules, module_a.py and module_b.py, with a circular dependency:

# module_a.py
from module_b import some_function_from_b

def function_from_a():
    print("Function from A")
    some_function_from_b()


# module_b.py
from module_a import function_from_a

def some_function_from_b():
    print("Function from B")
    function_from_a()

This will cause an ImportError. To fix it, you can move the call to function_from_a inside a function in module_b.py:

# module_a.py
def function_from_a():
    print("Function from A")


# module_b.py
from module_a import function_from_a

def some_function_from_b():
    print("Function from B")
    function_from_a()

Final Thoughts

ImportErrors due to circular dependencies can be tricky, but with a systematic approach, you can nail them. Remember to check for filename conflicts, restructure your imports, and use virtual environments to keep your projects clean. By following these steps, you should be able to resolve the ImportError and get back to extracting keywords with pke_zh!

Hope this helps, and happy coding!