NLTK is described as 'leading platform for building Python programs to work with human language data' and is an app in the Development category. There are eight alternatives to NLTK for a variety of platforms, including Self-Hosted solutions, Python, SaaS, Scala and Java. The best alternative is NLP Cloud, which is free. Other great apps like NLTK are TextBlob (Free, Open Source), Polyglot NLP (Free, Open Source), OpenNLP (Free, Open Source) and PyNLPl (Free, Open Source).
High performance NLP API based on spaCy and HuggingFace transformers, for Named Entity Recognition (NER), sentiment-analysis, classification, summarization, and more. You can either use the pre-trained models or upload your own custom models.
TextBlob is a Python (2 and 3) library for processing textual data. It provides a simple API for diving into common natural language processing (NLP) tasks such as part-of-speech tagging, noun phrase extraction, sentiment analysis, classification, translation, and more.
Polyglot is a natural language pipeline for Python that supports massive multilingual applications. Polyglot depends on pycld2 library which in turn depends on cld2 library for detecting language(s) used in plain text.
PyNLPl is a Python library for Natural Language Processing. It contains various modules useful for common, and less common, NLP tasks. PyNLPl can be used for basic tasks such as the extraction of n-grams and frequency lists, and to build simple language model.
spaCy is a leading NLP toolkit for Python. It's designed to help you do real work — to build real products, or gather real insights. The library respects your time, and tries to avoid wasting it. It's easy to install, and its API is simple and productive.