NameError: 名称 ‘nltk’ 未在 Python 中定义

# 👇️ in a virtual environment or using Python 2
pip install nltk

# 👇️ for python 3 (could also be pip3.10 depending on your version)
pip3 install nltk

# 👇️ if you get permissions error
sudo pip3 install nltk

# 👇️ if you don't have pip in your PATH environment variable
python -m pip install nltk

# 👇️ for python 3 (could also be pip3.10 depending on your version)
python3 -m pip install nltk

# 👇️ for Anaconda
conda install -c anaconda nltk

# ✅ import nltk first
import nltk

# 👇️ download nltk libraries if necessary
nltk.download()

sentence = """At eight o'clock on Thursday morning
 Arthur didn't feel very good."""

tokens = nltk.word_tokenize(sentence)

print(tokens)