为何Jupyter Notebook运行代码时提示ModuleNotFoundError: No module named 'wtforms'？

Alright, let’s break down exactly what’s causing this error when you run from wtforms import Form, StringField, validators in your notebook:

• wtforms isn’t installed in the Python environment Jupyter is using
  This is the #1 culprit. You might have installed wtforms via pip in your terminal, but Jupyter could be running a totally separate Python environment—like a Conda virtual env, a venv you set up for your project, or even a different Python version (3.8 vs 3.10, for example). These environments don’t share installed packages, so Jupyter can’t find the module you thought you installed.

• The installation failed (or you ran it in the wrong place)
  Maybe you tried installing wtforms but the process threw an error you missed (network issues, missing system dependencies, etc.), so the package never actually got added. Or you ran the pip install wtforms command in a terminal window linked to a different environment than the one Jupyter’s using.

• Permission issues messed up the installation
  If you installed wtforms without adding the --user flag and don’t have admin/sudo access, the package might have ended up in a system directory that Jupyter doesn’t have permission to access. Alternatively, it might be in your user directory but Jupyter’s environment isn’t configured to look there for packages.

• Jupyter’s using the wrong kernel for your project
  If you set up a custom virtual environment for this project, you need to register that environment as a Jupyter kernel. If you skipped that step, Jupyter will default to its base environment—and that base env almost certainly doesn’t have wtforms installed unless you explicitly added it there.

内容的提问来源于stack exchange，提问作者Steven123452