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

If you are working with Python and trying to use the scipy library, you may encounter the “NameError: name ‘scipy’ is not defined” error. In this tutorial, we will explore why this error occurs and the steps required to fix it so 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 'scipy' is not defined error occur?

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

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

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

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

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

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

The scipy module is not imported

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

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

# note that scipy is not imported

# create a matrix
matrix = scipy.array([[1, 2], [3, 4]])
# get the inverse matrix
inv_matrix = scipy.linalg.inv(matrix)

# print the inverse matrix
print(inv_matrix)

Output:

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

NameError                                 Traceback (most recent call last)

Cell In[1], line 4
      1 # note that scipy is not imported
      2 
      3 # create a matrix
----> 4 matrix = scipy.array([[1, 2], [3, 4]])
      5 # get the inverse matrix
      6 inv_matrix = scipy.linalg.inv(matrix)

NameError: name 'scipy' is not defined

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

import scipy

# create a matrix
matrix = scipy.array([[1, 2], [3, 4]])
# get the inverse matrix
inv_matrix = scipy.linalg.inv(matrix)

# print the inverse matrix
print(inv_matrix)

Output:

[[-2.   1. ]
 [ 1.5 -0.5]]

Here, we are importing the scipy module first and then using it. You can see that we did not get any errors here.

Note that instead of importing the entire scipy library, you can also import only specific parts of the library that you need. For example, in the above code, we can use the import statements from scipy import array and from scipy.linalg import inv and use the functions using their names.

The scipy module is imported using a different name

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

Let’s look at an example.

import scipy as sp

# create a matrix
matrix = scipy.array([[1, 2], [3, 4]])
# get the inverse matrix
inv_matrix = scipy.linalg.inv(matrix)

# print the inverse matrix
print(inv_matrix)

Output:

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

NameError                                 Traceback (most recent call last)

Cell In[1], line 4
      1 import scipy as sp
      3 # create a matrix
----> 4 matrix = scipy.array([[1, 2], [3, 4]])
      5 # get the inverse matrix
      6 inv_matrix = scipy.linalg.inv(matrix)

NameError: name 'scipy' is not defined

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

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

import scipy as sp

# create a matrix
matrix = sp.array([[1, 2], [3, 4]])
# get the inverse matrix
inv_matrix = sp.linalg.inv(matrix)

# print the inverse matrix
print(inv_matrix)

Output:

[[-2.   1. ]
 [ 1.5 -0.5]]

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

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

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

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

import scipy

# create a matrix
matrix = sp.array([[1, 2], [3, 4]])
# get the inverse matrix
inv_matrix = sp.linalg.inv(matrix)

# print the inverse matrix
print(inv_matrix)

Output:

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

NameError                                 Traceback (most recent call last)

Cell In[1], line 4
      1 import scipy
      3 # create a matrix
----> 4 matrix = sp.array([[1, 2], [3, 4]])
      5 # get the inverse matrix
      6 inv_matrix = sp.linalg.inv(matrix)

NameError: name 'sp' is not defined

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

import scipy as sp

# create a matrix
matrix = sp.array([[1, 2], [3, 4]])
# get the inverse matrix
inv_matrix = sp.linalg.inv(matrix)

# print the inverse matrix
print(inv_matrix)

Output:

[[-2.   1. ]
 [ 1.5 -0.5]]

We don’t get an error now.

Conclusion

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

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