How to Fix – NameError: name ‘numpy’ is not defined

If you are working with Python and trying to use the numpy library, you may encounter the “NameError: name ‘numpy’ is not defined” error. In this tutorial, we will explore why this error occurs and the steps required to fix it such that your Python code can successfully run without errors.

We will cover common causes of the error and provide solutions to help you get your code up and running quickly. So, let’s get started!

Why does the NameError: name 'numpy' is not defined error occur?

This error occurs when you try to use the numpy library in your Python code, but Python cannot find the numpy module in its namespace. The following are some of the scenarios in which this error usually occurs.

1. You have not imported the numpy module.
2. You have imported the numpy module using a different name.

How to fix the NameError: name 'numpy' is not defined?

Before we proceed with the above scenario and their solutions, make sure that you have the numpy module installed. If numpy is not installed and you try to import it, you’ll get a ModuleNotFoundError. Alternatively, you can check if you have numpy installed by running pip list in your terminal or command prompt. If numpy is not listed, install it by running pip install numpy.

If you are using a virtual environment or a different Python environment, make sure numpy is installed in that environment. You can activate the environment and run pip list to check if numpy is installed.

Let’s now look at the above scenarios in detail.

The numpy module is not imported

It can happen that you are trying to use the numpy module without even importing it. This is because Python does not recognize the numpy library and its functions until it is imported into the code.

For example, let’s try to use numpy without importing it and see what we get.

# note that numpy is not imported

# create an array
ar = numpy.array([1, 2, 3, 4])
# print the array
print(ar)

Output:

---------------------------------------------------------------------------

NameError                                 Traceback (most recent call last)

Cell In[1], line 4
      1 # note that numpy is not imported
      2 
      3 # create an array
----> 4 ar = numpy.array([1, 2, 3, 4])
      5 # print the array
      6 print(ar)

NameError: name 'numpy' is not defined

We get a NameError stating that the name numpy is not defined. To use numpy, you need to import it first.

import numpy

# create an array
ar = numpy.array([1, 2, 3, 4])
# print the array
print(ar)

Output:

[1 2 3 4]

Here, we are importing the numpy module first and then using it. You can see that we did not get any errors here.
Note that generally people use the import numpy as np statement to import the numpy module with the alias np.

The numpy module is imported using a different name

If you import the numpy module using a different name, for example import numpy as np, and then try to use the name “numpy” to use it, you will get a NameError because the name “numpy” is not defined in your current namespace.

Let’s look at an example.

import numpy as np

# create an array
ar = numpy.array([1, 2, 3, 4])
# print the array
print(ar)

Output:

---------------------------------------------------------------------------

NameError                                 Traceback (most recent call last)

Cell In[1], line 4
      1 import numpy as np
      3 # create an array
----> 4 ar = numpy.array([1, 2, 3, 4])
      5 # print the array
      6 print(ar)

NameError: name 'numpy' is not defined

We get a NameError: name 'numpy' is not defined. This is because we have imported the numpy module with the name np but we’re trying to use it using the name numpy.

To fix this error, you can either access numpy using the name that you have used in the import statement or import numpy without an alias.

import numpy as np

# create an array
ar = np.array([1, 2, 3, 4])
# print the array
print(ar)

Output:

[1 2 3 4]

In the above example, we are importing numpy as np and then using np to access the numpy module’s methods.

Alternatively, as seen in the example in the previous section, you can import numpy without any aliases and simply use numpy to avoid the NameError.

How to fix the NameError: name 'np' is not defined error?

You can similarly get the NameError: name 'np' is not defined if you’ve not used np as the name for numpy while importing it. For example.

import numpy

# create an array
ar = np.array([1, 2, 3, 4])
# print the array
print(ar)

Output:

---------------------------------------------------------------------------

NameError                                 Traceback (most recent call last)

Cell In[1], line 4
      1 import numpy
      3 # create an array
----> 4 ar = np.array([1, 2, 3, 4])
      5 # print the array
      6 print(ar)

NameError: name 'np' is not defined

We get this error because the name np does not exit in the namespace. To fix this error, use the import statement import numpy as np.

import numpy as np

# create an array
ar = np.array([1, 2, 3, 4])
# print the array
print(ar)

Output:

[1 2 3 4]

We don’t get an error now.

Conclusion

In conclusion, the “NameError: name ‘numpy’ is not defined” error can occur due to two scenarios – numpy is not imported or numpy is imported with a different name. If numpy is not imported, you can simply import it using the command import numpy. On the other hand, if numpy is imported with a different name, for example, import numpy as np you can use “np” to use numpy methods. By following these steps, you can easily fix the “NameError: name ‘numpy’ is not defined” error and continue with your computation tasks utilizing numpy.

You might also be interested in –

• How to Fix – NameError: name ‘pandas’ is not defined
• Find the shortest word in a List in Python (with examples)
• Count Unique Values in a Numpy Array