DocArray supports many different modalities including tabular data. This section will show you how to load and handle tabular data using DocArray.

A common way to store tabular data is via CSV (comma-separated values) files. You can load such data from a given CSV file into a [DocList][docarray.DocList].

Let's take a look at the following example file, which includes data about books and their authors and year of publication:

title,author,year
Harry Potter and the Philosopher's Stone,J. K. Rowling,1997
Klara and the sun,Kazuo Ishiguro,2020
A little life,Hanya Yanagihara,2015

First, define the Document schema describing the data:

from docarray import BaseDoc


class Book(BaseDoc):
    title: str
    author: str
    year: int

Next, load the content of the CSV file to a [DocList][docarray.DocList] instance of Books via [.from_csv()][docarray.array.doc_list.io.IOMixinDocList.from_csv]:

from docarray import DocList


docs = DocList[Book].from_csv(
    file_path='https://github.com/docarray/docarray/blob/main/tests/toydata/books.csv?raw=true'
)
docs.summary()

The resulting [DocList][docarray.DocList] object contains three Books, since each row of the CSV file corresponds to one book and is assigned to one Book instance.

Vice versa, you can also store your [DocList][docarray.DocList] data in a .csv file using [.to_csv()][docarray.array.doc_list.io.IOMixinDocList.to_csv]:

docs.to_csv(file_path='/path/to/my_file.csv')

Tabular data is often not the best choice to represent nested Documents. Hence, nested Documents will be stored flattened and can be accessed by their '__'-separated access paths.

Let's take a look at an example. We now want to store not only the book data but moreover book review data. To do so, we define a BookReview class that has a nested book attribute as well as the non-nested attributes n_ratings and stars:

class BookReview(BaseDoc):
    book: Book
    n_ratings: int
    stars: float


review_docs = DocList[BookReview](
    [BookReview(book=book, n_ratings=12345, stars=5) for book in docs]
)
review_docs.summary()

As expected all nested attributes will be stored by their access path:

review_docs.to_csv(file_path='/path/to/nested_documents.csv')

id,book__id,book__title,book__author,book__year,n_ratings,stars
d6363aa3b78b4f4244fb976570a84ff7,8cd85fea52b3a3bc582cf56c9d612cbb,Harry Potter and the Philosopher's Stone,J. K. Rowling,1997,12345,5.0
5b53fff67e6b6cede5870f2ee09edb05,87b369b93593967226c525cf226e3325,Klara and the sun,Kazuo Ishiguro,2020,12345,5.0
addca0475756fc12cdec8faf8fb10d71,03194cec1b75927c2259b3c0fff1ab6f,A little life,Hanya Yanagihara,2015,12345,5.0

Not only can you load and save comma-separated values (CSV) data, but also tab-separated values (TSV), by adjusting the dialect parameter in [.from_csv()][docarray.array.doc_list.io.IOMixinDocList.from_csv] and [.to_csv()][docarray.array.doc_list.io.IOMixinDocList.to_csv].

The dialect defaults to 'excel', which refers to comma-separated values. For tab-separated values, you can use 'excel-tab'.

Let's take a look at what this would look like with a tab-separated file:

title	author	year
Title1	author1	2020
Title2	author2	1234

docs = DocList[Book].from_csv(
    file_path='https://github.com/docarray/docarray/blob/main/tests/toydata/books.tsv?raw=true',
    dialect='excel-tab',
)
for doc in docs:
    doc.summary()

Great! All the data is correctly read and stored in Book instances.

If your values are separated by yet another separator, you can create your own class that inherits from csv.Dialect. Within this class, you can define your dialect's behavior by setting the provided formatting parameters.

For instance, let's assume you have a semicolon-separated table:

first_name;last_name;year
Jane;Austin;2020
John;Doe;1234

Now, let's define our SemicolonSeparator class. Next to the delimiter parameter, we have to set some more formatting parameters such as doublequote and lineterminator.

import csv


class SemicolonSeparator(csv.Dialect):
    delimiter = ';'
    doublequote = True
    lineterminator = '\r\n'
    quotechar = '"'
    quoting = csv.QUOTE_MINIMAL

Finally, you can load your data by setting the dialect parameter in [.from_csv()][docarray.array.doc_list.io.IOMixinDocList.from_csv] to an instance of your SemicolonSeparator.

docs = DocList[Book].from_csv(
    file_path='https://github.com/docarray/docarray/blob/main/tests/toydata/books_semicolon_sep.csv?raw=true',
    dialect=SemicolonSeparator(),
)
for doc in docs:
    doc.summary()