How to Fix – NameError name ‘wordnet’ is not defined

WordNet is a lexical database for the English language, which is included in the Natural Language Toolkit (NLTK) corpus in Python. It provides a large collection of words and their relationships, such as synonyms, antonyms, hypernyms, hyponyms, and meronyms. It is often used in natural language processing tasks such as text classification, sentiment analysis, and information retrieval. The NLTK library provides a wordnet corpus that you can use in your Python code. It can happen that when you’re trying to use wordnet from the NLTK library, you may run into the “NameError: name ‘wordnet’ is not defined”.

In this tutorial, we will discuss how to fix this error by importing the wordnet module correctly. By the end of this tutorial, you will have a better understanding of how to import the wordnet module from the NLTK library and avoid common errors.

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

This error occurs when you try to use the wordnet module from the NLTK library in your Python code, but Python cannot find the wordnet module in its namespace. This could happen if you are not correctly importing the wordnet module.

How to correctly import wordnet?

The correct way to import the wordnet module is as follows –

1. Make sure that you have the nltk module installed. Use pip show nltk inside command prompt or terminal to check if you have the nltk module installed or not. If it is not installed, use pip install nltk inside the command prompt or terminal to install the nltk module.

2. Import the nltk module.

3. Download the wordnet corpus using the nltk module using the command nltk.download('wordnet'). This will download the wordnet corpus to your computer.

4. After downloading the wordnet corpus, you can import the wordnet module in your Python code using from nltk.corpus import wordnet

The above steps will make sure that you have correctly imported wordnet from the nltk module. Let’s now look at an example of importing and using the wordnet module from the nltk library.

Assuming that the nltk module is installed.

import nltk

# download the wordnet corpus
nltk.download('wordnet')

# import wordnet
from nltk.corpus import wordnet

# get synonyms for the word "happy"
synonyms = []
for syn in wordnet.synsets("happy"):
    for lemma in syn.lemmas():
        synonyms.append(lemma.name())

# print the list of synonyms
print(synonyms)

Output:

[nltk_data] Downloading package wordnet to /Users/piyush/nltk_data...

['happy', 'felicitous', 'happy', 'glad', 'happy', 'happy', 'well-chosen']

In the above example, we are printing the synonyms for the word “happy” using the wordnet module from nltk. Note that WordNet groups words into sets of synonyms called “synsets”, and each synset contains a list of lemmas (i.e., words with the same meaning). In this example, we loop through all the synsets for the word “happy” and add the lemma names to a list of synonyms.

We followed the steps mentioned earlier and thus didn’t get an error.

Common Errors when importing wordnet

Let’s now look at some common scenarios that could result in errors while importing the wordnet module.

NameError: name 'wordnet' is not defined

A common mistake people do is that they download the wordnet corpus but forget to import it. Like in the example below –

import nltk

# download the wordnet corpus
nltk.download('wordnet')

# get synonyms for the word "happy"
synonyms = []
for syn in wordnet.synsets("happy"):
    for lemma in syn.lemmas():
        synonyms.append(lemma.name())

# print the list of synonyms
print(synonyms)

Output:

[nltk_data] Downloading package wordnet to /Users/piyush/nltk_data...

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

NameError                                 Traceback (most recent call last)

Cell In[1], line 8
      6 # get synonyms for the word "happy"
      7 synonyms = []
----> 8 for syn in wordnet.synsets("happy"):
      9     for lemma in syn.lemmas():
     10         synonyms.append(lemma.name())

NameError: name 'wordnet' is not defined

Using nltk.download('wordnet') will download the wordnet corpus to your computer but in order to use it in your Python code, you still have to import the wordnet module. You can import the wordnet module using from nltk.corpus import wordnet.

LookupError: resource 'wordnet' was not found

If the wordnet corpus is not downloaded on your machine and you try to import the wordnet, it will give you a LookupError.

import nltk

# import wordnet
from nltk.corpus import wordnet

# get synonyms for the word "happy"
synonyms = []
for syn in wordnet.synsets("happy"):
    for lemma in syn.lemmas():
        synonyms.append(lemma.name())

# print the list of synonyms
print(synonyms)

Output:

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

LookupError: 
**********************************************************************
  Resource wordnet not found.
  Please use the NLTK Downloader to obtain the resource:

  >>> import nltk
  >>> nltk.download('wordnet')

**********************************************************************

To avoid this error, make sure that the wordnet corpus is downloaded before you import it into your code.

Conclusion

In conclusion, the “NameError name ‘wordnet’ is not defined” error can be frustrating when working with natural language processing tasks. However, by following the steps outlined in this tutorial, you can easily fix this error and continue with your NLP project. Remember to import the necessary libraries and modules, and ensure that you have installed the required packages. With these simple fixes, you can overcome this error and successfully complete your NLP tasks.

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