NameError: name 'nan' is not defined in Python

NameError: name 'nan' is not defined in Python #

The Python "NameError: name 'nan' is not defined" occurs when we use the nan variable from numpy without importing it. To solve the error, make sure to install numpy and import nan (from numpy import nan).

Open your terminal in your project's root directory and install the numpy module.

Copied!
# 👇️ in a virtual environment or using Python 2
pip install numpy

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

# 👇️ if you get permissions error
sudo pip3 install numpy

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

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

# 👇️ for Anaconda
conda install -c anaconda numpy

After installing numpy, you can import the nan variable.

Copied!
from numpy import nan, log

print(nan)

print(log([-1, 1, 2]))  # array([        NaN,  0.        ,  0.69314718])

The import statement shows how to import nan and log from numpy.

The nan variable returns a floating point representation of Not a Number.

Note that NaN and NAN are aliases of nan.

Alternatively, you can import the entire numpy module and access nan as a property.

Copied!
import numpy as np

print(np.nan)

print(np.log([-1, 1, 2]))  # array([        NaN,  0.        ,  0.69314718])

We imported the entire numpy module and aliased it to np, so you would access the nan variable as np.nan.

Also, make sure you haven't imported numpy 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 'nan' is not defined" occurs when we use the nan variable from numpy without importing it. To solve the error, make sure to install numpy and import nan (from numpy import nan).