Sous-ensemble d’un DataFrame

Introduction à Polars

Liam Brannigan

Data Scientist and Polars Contributor

Sélectionner des lignes

rentals[0]

shape: (1, 8)
| name      | type    | price | bedrooms | doubles | singles | review | beach |
| ---       | ---     | ---   | ---      | ---     | ---     | ---    | ---   |
| str       | str     | i64   | i64      | i64     | i64     | f64    | bool  |
|-----------|---------|-------|----------|---------|---------|--------|-------|
| Seashells | Cottage | 540   | 4        | 2       | 2       | 8.7    | true  |

Sélectionner des lignes

rentals[-1]

shape: (1, 8)
| name                | type    | price | bedrooms | doubles | singles | review | beach |
| ---                 | ---     | ---   | ---      | ---     | ---     | ---    | ---   |
| str                 | str     | i64   | i64      | i64     | i64     | f64    | bool  |
|---------------------|---------|-------|----------|---------|---------|--------|-------|
| Tehidy Holiday Park | Cottage | 637   | 4        | 2       | 4       | 9.0    | false |

Sélectionner une plage de lignes

rentals[1:3]

shape: (2, 8)
| name      | type    | price | bedrooms | doubles | singles | review | beach |
| ---       | ---     | ---   | ---      | ---     | ---     | ---    | ---   |
| str       | str     | i64   | i64      | i64     | i64     | f64    | bool  |
|-----------|---------|-------|----------|---------|---------|--------|-------|
| Seashells | Cottage | 540   | 4        | 2       | 2       | 8.7    | true  |
| Lake view | Cottage | 714   | 3        | 1       | 4       | 9.2    | true  |

Créer une Series à partir d’une colonne de DataFrame

rentals["name"]

shape: (2,)
Series: 'name' [str]
[
    "Waves"
    "Seashells"
]

Une seule colonne dans [] produit une Series
Series utile pour les visualisations

Sélectionner plusieurs colonnes avec des crochets

rentals[["name", "price"]]

shape: (5, 2)
| name        | price |
| ---         | ---   |
| str         | i64   |
|-------------|-------|
| Waves       | 540   |
| Seashells   | 540   |
| Lake view   | 714   |
| Piran View  | 775   |
| Palma Villa | 1772  |

Sélectionner des lignes et des colonnes

rentals[:3, ["name", "price"]]

shape: (3, 2)
| name      | price |
| ---       | ---   |
| str       | i64   |
|-----------|-------|
| Waves     | 540   |
| Seashells | 540   |
| Lake view | 714   |

Sous-ensemble de colonnes avec .select()

rentals.select("name", "price")

shape: (3, 2)
| name        | price |
| ---         | ---   |
| str         | i64   |
|-------------|-------|
| Waves       | 540   |
| Seashells   | 540   |
| Lake view   | 714   |

df.select(["name", "price"])

Crochets ou select ?

rentals.select("name","price")

shape: (3, 2)
| name        | price |
| ---         | ---   |
| str         | i64   |
|-------------|-------|
| Waves       | 540   |
| Seashells   | 540   |
| Lake view   | 714   |

.select() permet des optimisations

rentals[["name","price"]]

shape: (3, 2)
| name        | price |
| ---         | ---   |
| str         | i64   |
|-------------|-------|
| Waves       | 540   |
| Seashells   | 540   |
| Lake view   | 714   |

Passons à la pratique !

Introduction à Polars