textblob

Breaks text into individual sentences using a pluggable SentenceTokenizer component that handles edge cases like abbreviations, ellipses, and decimal points. The tokenizer uses pattern-based rules and optional NLTK integration to identify sentence boundaries without requiring external API calls, enabling offline processing of large text volumes.

Tokenizes text into individual words using a WordTokenizer component that preserves contractions, handles punctuation attachment, and creates Word objects with lazy-loaded morphological properties. The architecture defers expensive operations like lemmatization and inflection until explicitly accessed, reducing memory overhead for large texts.

Provides a hierarchical object model where TextBlob contains Sentences, which contain Words, enabling intuitive navigation and analysis at multiple granularities. Users can access text at document, sentence, or word level through nested object properties, with each level providing relevant methods (e.g., .sentiment on TextBlob/Sentence, .lemma on Word). The architecture maintains bidirectional references between levels, enabling context-aware analysis.

Assigns grammatical parts of speech (noun, verb, adjective, etc.) to each word using a pluggable POS tagger component with multiple implementations: NLTKTagger (using NLTK's averaged perceptron model) and PatternTagger (using Pattern library's rules). The architecture allows runtime selection of taggers and custom implementations via dependency injection, enabling trade-offs between accuracy and speed.

Extracts noun phrases (multi-word noun groups like 'the quick brown fox') from sentences using pluggable NP extractor components: FastNPExtractor (pattern-based using POS tag sequences) and ConllExtractor (statistical model trained on CoNLL data). The extractors operate on POS-tagged text and identify contiguous noun phrase chunks based on grammar patterns or learned models.

Analyzes the emotional tone of text by computing two independent scores: polarity (ranging from -1.0 for negative to +1.0 for positive) and subjectivity (ranging from 0.0 for objective to 1.0 for subjective). The implementation uses a lexicon-based approach backed by the Pattern library, which maintains a dictionary of words with pre-computed sentiment scores and aggregates them across the text with optional intensity modifiers (negation, intensifiers).

Transforms words between different morphological forms (singular/plural, base/past tense, comparative/superlative) using rule-based morphological operations backed by the Pattern library. The Word class provides methods like .singularize(), .pluralize(), .lemmatize() that apply linguistic rules and exception dictionaries to generate correct inflected forms without requiring a full morphological analyzer.

Corrects misspelled words by generating candidate corrections using edit distance (Levenshtein distance) and ranking them by word frequency in a reference corpus. The correct() method operates on TextBlob or Sentence objects and replaces misspelled words with the highest-ranked correction, using a pre-built frequency dictionary to prefer common words over rare ones.

Trains and applies custom text classifiers using a Naive Bayes algorithm that learns word-feature associations from labeled training examples. The Classifier class extracts features (word presence/absence) from text and learns conditional probabilities of class labels given features, enabling domain-specific text categorization without external ML libraries.

Provides a Blobber factory class that creates TextBlob instances with consistent, customizable configurations for tokenizers, POS taggers, and NP extractors. The factory pattern enables dependency injection of alternative component implementations at instantiation time, allowing users to swap between fast and accurate implementations or inject custom components without modifying TextBlob core code.

Implements lazy evaluation of expensive NLP operations by deferring computation until properties are explicitly accessed. Sentence objects don't compute POS tags until .tags is accessed, Word objects don't compute lemmas until .lemma is accessed, and sentiment analysis only runs when .sentiment is accessed. This architecture reduces memory overhead and computation time for large texts where only a subset of analyses are needed.