# Welcome to arrowdantic
Arrowdantic is a small Python library backed by a
[mature Rust implementation](https://github.com/jorgecarleitao/arrow2) of Apache Arrow
that can interoperate with
* [Parquet](https://parquet.apache.org/)
* [Apache Arrow](https://arrow.apache.org/) and
* [ODBC](https://en.wikipedia.org/wiki/Open_Database_Connectivity) (databases).
For simple (but data-heavy) data engineering tasks, this package essentially replaces
`pyarrow`: it supports reading from and writing to Parquet, Arrow at the same or
higher performance and higher safety (e.g. no segfaults).
Furthermore, it supports reading from and writing to ODBC compliant databases at
the same or higher performance than [`turbodbc`](https://turbodbc.readthedocs.io/en/latest/).
This package is particularly suitable for environments such as AWS Lambda -
it takes 8M of disk space, compared to 82M taken by pyarrow.
## Features
* declare and access Arrow-backed arrays (integers, floats, boolean, string, binary)
* read from and write to Apache Arrow IPC file
* read from and write to Apache Parquet
* read from and write to ODBC-compliant databases (e.g. postgres, mongoDB)
## Examples
### Use parquet
```python
import io
import arrowdantic as ad
original_arrays = [ad.UInt32Array([1, None])]
schema = ad.Schema(
[ad.Field(f"c{i}", array.type, True) for i, array in enumerate(original_arrays)]
)
data = io.BytesIO()
with ad.ParquetFileWriter(data, schema) as writer:
writer.write(ad.Chunk(original_arrays))
data.seek(0)
reader = ad.ParquetFileReader(data)
chunk = next(reader)
assert chunk.arrays() == original_arrays
```
### Use Arrow files
```python
import arrowdantic as ad
original_arrays = [ad.UInt32Array([1, None])]
schema = ad.Schema(
[ad.Field(f"c{i}", array.type, True) for i, array in enumerate(original_arrays)]
)
import io
data = io.BytesIO()
with ad.ArrowFileWriter(data, schema) as writer:
writer.write(ad.Chunk(original_arrays))
data.seek(0)
reader = ad.ArrowFileReader(data)
chunk = next(reader)
assert chunk.arrays() == original_arrays
```
### Use ODBC
```python
import arrowdantic as ad
arrays = [ad.Int32Array([1, None]), ad.StringArray(["aa", None])]
with ad.ODBCConnector(r"Driver={SQLite3};Database=sqlite-test.db") as con:
# create an empty table with a schema
con.execute("DROP TABLE IF EXISTS example;")
con.execute("CREATE TABLE example (c1 INT, c2 TEXT);")
# insert the arrays
con.write("INSERT INTO example (c1, c2) VALUES (?, ?)", ad.Chunk(arrays))
# read the arrays
with con.execute("SELECT c1, c2 FROM example", 1024) as chunks:
assert chunks.fields() == [
ad.Field("c1", ad.DataType.int32(), True),
ad.Field("c2", ad.DataType.string(), True),
]
chunk = next(chunks)
assert chunk.arrays() == arrays
```
### Use timezones
This package fully supports datetime and conversions between them and arrow:
```python
import arrowdantic as ad
dt = datetime.datetime(
year=2021,
month=1,
day=1,
hour=1,
minute=1,
second=1,
microsecond=1,
tzinfo=datetime.timezone.utc,
)
a = ad.TimestampArray([dt, None])
assert (
str(a)
== 'Timestamp(Microsecond, Some("+00:00"))[2021-01-01 01:01:01.000001 +00:00, None]'
)
assert list(a) == [dt, None]
assert a.type == ad.DataType.timestamp(datetime.timezone.utc)
```
