NameError：名称“plt”未在 Python 中定义

NameError：名称“plt”未在 Python 中定义

NameError: name ‘plt’ is not defined in Python

Python“NameError: name ‘plt’ is not defined”发生在我们使用
pyplot模块而不先导入它时。要解决该错误，请在使用前安装
matplotlib并导入plt( import matplotlib.pyplot as plt)。

在项目的根目录中打开终端并安装matplotlib
模块。

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

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

# 👇️ if you get permissions error
sudo pip3 install matplotlib

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

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

# 👇️ alternative for Ubuntu/Debian
sudo apt-get install python3-matplotlib

# 👇️ alternative for CentOS
sudo yum install python3-matplotlib

# 👇️ alternative for Fedora
sudo yum install python3-matplotlib

# 👇️ for Anaconda
conda install -c conda-forge matplotlib

安装matplotlib模块后，确保pyplot在使用前导入它。

# 👇️ import pyplot and alias it as plt
import matplotlib.pyplot as plt

fig, ax = plt.subplots()

print(fig)
print(ax)

我们使用别名从as导入pyplot模块。matplotlibplt

We imported matplotlib.pyplot and aliased it to plt, so you would access any
pyplot methods as plt.plot(), plt.ylabel(), plt.show(), etc.

Make sure you haven’t misspelled the module you are importing because module
names are case-sensitive.

Also, make sure you haven’t placed your import statement in a nested scope, e.g.
a function. Import the module at the top level to be able to use it throughout
your code.

Conclusion #

The Python “NameError: name ‘plt’ is not defined” occurs when we use the
pyplot module without importing it first. To solve the error, install
matplotlib and import plt (import matplotlib.pyplot as plt) before using
it.