Creating tables

From data in memory

column_names = ['letter', 'number']
column_types = [agate.Text(), agate.Number()]

rows = [
    ('a', 1),
    ('b', 2),
    ('c', None)
]

table = agate.Table(rows, column_names, column_types)

From a CSV

By default, loading a table from a CSV will use agate’s builtin TypeTester to infer column types:

table = agate.Table.from_csv('filename.csv')

Override type inference

In some cases agate’s TypeTester may guess incorrectly. To override the type for a column construct a TypeTester manually and use the force argument:

tester = agate.TypeTester(force={
    'column_name': agate.Text()
})

table = agate.Table.from_csv('filename.csv', column_types=tester)

Limit type inference

For large datasets TypeTester may be unreasonably slow. In order to limit the amount of data it uses you can specify the limit argument. Note that if data after the limit invalidates the TypeTester’s inference you may get errors when the data is loaded.

tester = agate.TypeTester(limit=100)

table = agate.Table.from_csv('filename.csv', column_types=tester)

Manually specify columns

If you know the types of your data you may find it more efficient to manually specify the names and types of your columns. This also gives you an opportunity to rename columns when you load them.

text_type = agate.Text()
number_type = agate.Number()

column_names = ['city', 'area', 'population']
column_types = [text_type, number_type, number_type]

table = agate.Table.from_csv('population.csv', column_names, column_types)

Or, you can use this method to load data from a file that does not have a header row:

table = agate.Table.from_csv('population.csv', column_names, column_types, header=False)

From a unicode CSV

You don’t have to do anything special. It just works!

From a latin1 CSV

table = agate.Table.from_csv('census.csv', encoding='latin1')

From JSON

table = agate.Table.from_json('filename.json')

From newline-delimited JSON

table = agate.Table.from_json('filename.json', newline=True)

From a SQL database

Use the agate-sql extension.

import agatesql

table = agate.Table.from_sql('postgresql:///database', 'input_table')