Fields

Basic Field Types

There are basic fields to support Python datatypes. A few have unique options that affect how the type casting process works:

class yankee.base.fields.Field(*args, default=None, **kwargs)

The basic field - performs no type casting

class yankee.base.fields.String(*args, formatter=None, null_value=None, **kwargs)

String Field

Always outputs a string value, or None

Parameters:

• formatter (Callable) – a callable for formatting the resulting string. Defaults to a newline-preserving whitespace cleaner

• null_value (str) – a string value to indicate that it should be None. Some data sources use a hyphen or other symbol rather than empty value

class yankee.base.fields.Integer(*args, formatter=None, null_value=None, **kwargs)

Float Field

Always outputs an integer value. If the value is a float, the result will be the result of calling int on the value.

class yankee.base.fields.Float(*args, formatter=None, null_value=None, **kwargs)

Float Field

Always outputs a float value

class yankee.base.fields.Boolean(*args, true_value='true', true_func=None, case_sensitive=False, allow_none=True, **kwargs)

Boolean Field

Always outputs a boolean value (True, or False)

Parameters:

• true_value (str) – a custom string value that should be considered truthy

• true_func (Callable) – a custom function that, when executed on the result, should return True or False

• case_sensitive (str) – if a true_value is provided, whether it should be considered case sensitive

• allow_none (str) – if the data key doesn’t find a match, and this is true, then it will return None rather than False

class yankee.base.fields.DateTime(*args, dt_format=None, dt_converter=False, **kwargs)

DateTime Field

Always outputs a datetime.datetime value. The initial value retrieved should be a string, which is then parsed as an isoformatted date. If that parsing fails, it uses dateutil.parser.parse to attempt to retrieve a datetime.

Parameters:

• dt_format (str) – a formatting string from datetime.datetime.strptime to use

• dt_converter (callable) – a custom function to parse a date, overriding the default

class yankee.base.fields.Date(*args, dt_format=None, dt_converter=False, **kwargs)

Date Field

Always outputs a datetime.date value. Uses the same args as DateTime

Special Field Types

There are also a few special types for common use cases

class yankee.base.fields.Const(const, output_type=None, *args, **kwargs)

Constant Field

Always outputs the provided constant value

Parameters:

const (any) – The constant value to return

class yankee.base.fields.Exists(*args, default=None, **kwargs)

Exists Field

Outputs true if the data item is present, else false

Schema-Like fields

There are more fields that behave a bit like Schemas, in that they have subfields:

class yankee.base.fields.Combine(*args, flatten=False, prefix=False, **kwargs)

Can have fields like a schema that are then passed as an object to a combine function that transforms it to a single string value

class yankee.base.fields.DelimitedString(item_schema, data_key=None, delimeter=',', **kwargs)

class yankee.base.fields.Dictionary(data_key, key: Field, value: Field, **kwargs)

class yankee.base.fields.Alternative(*args, flatten=False, prefix=False, **kwargs)

There may be a piece of data that has different names in different contexts. This has fields like a schema, then passes as a value the first non-empty or non-null result