Sottoinsiemi di un DataFrame
Introduzione a Polars
Liam Brannigan
Data Scientist and Polars Contributor
Selezionare righe
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 |
Selezionare righe
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 |
Selezionare un intervallo di righe
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 |
Creare una Series da una colonna del DataFrame
rentals["name"]
shape: (2,)
Series: 'name' [str]
[
"Waves"
"Seashells"
]
- Singola colonna in
[]restituisce unaSeries Seriesutile per le visualizzazioni
Selezionare più colonne con le parentesi
rentals[["name", "price"]]
shape: (5, 2)
| name | price |
| --- | --- |
| str | i64 |
|-------------|-------|
| Waves | 540 |
| Seashells | 540 |
| Lake view | 714 |
| Piran View | 775 |
| Palma Villa | 1772 |
Selezionare righe e colonne
rentals[:3, ["name", "price"]]
shape: (3, 2)
| name | price |
| --- | --- |
| str | i64 |
|-----------|-------|
| Waves | 540 |
| Seashells | 540 |
| Lake view | 714 |
Sottoinsiemi di colonne con .select()
rentals.select("name", "price")
shape: (3, 2)
| name | price |
| --- | --- |
| str | i64 |
|-------------|-------|
| Waves | 540 |
| Seashells | 540 |
| Lake view | 714 |
df.select(["name", "price"])
Brackets o select?
rentals.select("name","price")
shape: (3, 2)
| name | price |
| --- | --- |
| str | i64 |
|-------------|-------|
| Waves | 540 |
| Seashells | 540 |
| Lake view | 714 |
.select() consente ottimizzazioni
rentals[["name","price"]]
shape: (3, 2)
| name | price |
| --- | --- |
| str | i64 |
|-------------|-------|
| Waves | 540 |
| Seashells | 540 |
| Lake view | 714 |
Passons à la pratique !
Introduzione a Polars
