March 2025
Intermediate to advanced
504 pages
12h 5m
Italian
Content preview from Python Polars: la guida definitiva
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Capitolo 7. Espressioni iniziali
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L'obiettivo di questo capitolo è quello di introdurre le espressioni, che sono ciò che rende l'API Polars così potente ed elegante. Questo capitolo costituisce la base per i restanti capitoli della Parte III, "Express", dove si approfondiscono le espressioni specifiche e il loro utilizzo.
Espressioni polari contro espressioni regolari
Le espressioni Polars non devono essere confuse con le espressioni regolari. Un'espressione regolare, o regex, è una sequenza di caratteri che viene utilizzata per abbinare il testo. Ad esempio, la regex [Pp](ol|and)ar?s corrisponde sia a pandas che a Polars, ma non a panda o polaris.
Alcuni metodi di Polars accettano le regex, come pl.col() per selezionare le colonne e Expr.str.replace() per sostituire i valori. Il sito web interattivo RegExr di Grant Skinner e il libro Introducing Regular Expressions di Michael Fitzgerald (O'Reilly) sono risorse utili per saperne di più sulle regex.
Leespressioni, in Polars, sono blocchi riutilizzabili che ti permettono di eseguire molte operazioni di gestione dei dati, tra cui la selezione di colonne esistenti, la creazione di nuove colonne, il filtraggio di righe in base a una condizione e il calcolo di aggregazioni. In breve, compaiono ovunque.
Le espressioni hanno così tanto da offrire che abbiamo diviso la loro trattazione in tre capitoli, ...
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