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

If you are a Python developer who has encountered the error message “NameError: name ‘re’ is not defined”, you are not alone. In this tutorial, we will explore the possible causes of this error and provide step-by-step instructions on how to fix it.

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 're' is not defined error occur?

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

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

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

The re module in Python is a built-in module that provides support for regular expressions. Regular expressions are a powerful tool for pattern matching and text processing. The re module allows you to search for patterns in strings, replace text, and split strings based on patterns. It provides a set of functions and methods that can be used to work with regular expressions in Python.

Since this module is part of the Python Standard Library, you don’t need to separately install it. You can simply import it and start using it.

Let’s now look at the above scenarios that may result into the above error in detail.

The re module is not imported

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

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

# note that the re module is not imported

# Define a string to search
text = "The quick brown fox jumps over the lazy dog."

# Define a regular expression pattern to search for
pattern = r"fox"

# Use the search() function to find the first occurrence of the pattern in the text
match = re.search(pattern, text)

# Print the result
if match:
    print("Found:", match.group())
else:
    print("Not found.")

Output:

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

NameError                                 Traceback (most recent call last)

Cell In[1], line 10
      7 pattern = r"fox"
      9 # Use the search() function to find the first occurrence of the pattern in the text
---> 10 match = re.search(pattern, text)
     12 # Print the result
     13 if match:

NameError: name 're' is not defined

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

import re

# Define a string to search
text = "The quick brown fox jumps over the lazy dog."

# Define a regular expression pattern to search for
pattern = r"fox"

# Use the search() function to find the first occurrence of the pattern in the text
match = re.search(pattern, text)

# Print the result
if match:
    print("Found:", match.group())
else:
    print("Not found.")

Output:

Found: fox

Here, we are importing the re module first and then using it to search for a string in a text. You can see that we did not get any errors here.

The re module is imported using a different name

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

Let’s look at an example.

import re as regex

# Define a string to search
text = "The quick brown fox jumps over the lazy dog."

# Define a regular expression pattern to search for
pattern = r"fox"

# Use the search() function to find the first occurrence of the pattern in the text
match = re.search(pattern, text)

# Print the result
if match:
    print("Found:", match.group())
else:
    print("Not found.")

Output:

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

NameError                                 Traceback (most recent call last)

Cell In[1], line 10
      7 pattern = r"fox"
      9 # Use the search() function to find the first occurrence of the pattern in the text
---> 10 match = re.search(pattern, text)
     12 # Print the result
     13 if match:

NameError: name 're' is not defined

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

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

Conclusion

In conclusion, encountering a NameError: name 're' is not defined error can be frustrating, but it is a common issue that can be easily fixed. By ensuring that the re module is imported correctly and that the correct syntax is used when calling its functions, you can avoid this error and successfully execute your code.

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