Field

class psynet.field.ImmutableVarStore(data)

Bases: BaseVarStore, dict

class psynet.field.PythonClass(*args, **kwargs)

Bases: PythonObject

property python_type

Return the Python type object expected to be returned by instances of this type, if known.

Basically, for those types which enforce a return type, or are known across the board to do such for all common DBAPIs (like int for example), will return that type.

If a return type is not defined, raises NotImplementedError.

Note that any type also accommodates NULL in SQL which means you can also get back None from any type in practice.

class psynet.field.PythonObject(*args, **kwargs)

Bases: TypeDecorator

impl

alias of String

process_bind_param(value, dialect)

Receive a bound parameter value to be converted.

Custom subclasses of _types.TypeDecorator should override this method to provide custom behaviors for incoming data values. This method is called at statement execution time and is passed the literal Python data value which is to be associated with a bound parameter in the statement.

The operation could be anything desired to perform custom behavior, such as transforming or serializing data. This could also be used as a hook for validating logic.

Parameters:

• value – Data to operate upon, of any type expected by this method in the subclass. Can be None.

• dialect – the Dialect in use.

See also

types_typedecorator

_types.TypeDecorator.process_result_value()

process_literal_param(value, dialect)

Receive a literal parameter value to be rendered inline within a statement.

Note

This method is called during the SQL compilation phase of a statement, when rendering a SQL string. Unlike other SQL compilation methods, it is passed a specific Python value to be rendered as a string. However it should not be confused with the _types.TypeDecorator.process_bind_param() method, which is the more typical method that processes the actual value passed to a particular parameter at statement execution time.

Custom subclasses of _types.TypeDecorator should override this method to provide custom behaviors for incoming data values that are in the special case of being rendered as literals.

The returned string will be rendered into the output string.

process_result_value(value, dialect)

Receive a result-row column value to be converted.

Custom subclasses of _types.TypeDecorator should override this method to provide custom behaviors for data values being received in result rows coming from the database. This method is called at result fetching time and is passed the literal Python data value that’s extracted from a database result row.

The operation could be anything desired to perform custom behavior, such as transforming or deserializing data.

Parameters:

• value – Data to operate upon, of any type expected by this method in the subclass. Can be None.

• dialect – the Dialect in use.

See also

types_typedecorator

_types.TypeDecorator.process_bind_param()

property python_type

Return the Python type object expected to be returned by instances of this type, if known.

Basically, for those types which enforce a return type, or are known across the board to do such for all common DBAPIs (like int for example), will return that type.

If a return type is not defined, raises NotImplementedError.

Note that any type also accommodates NULL in SQL which means you can also get back None from any type in practice.

class psynet.field.VarStore(owner)

Bases: BaseVarStore

A repository for arbitrary variables which will be serialized to JSON for storage into the database, specifically in the details field. Variables can be set with the following syntax: participant.var.my_var_name = "value_to_set". The variable can then be accessed with participant.var.my_var_name. See the methods below for an alternative API.

TIP 1: the standard setter function is unavailable in lambda functions, which are otherwise convenient to use when defining e.g. CodeBlock objects. Use psynet.field.VarStore.set() instead, for example:

from psynet.timeline import CodeBlock

CodeBlock(lambda participant: participant.var.set("my_var", 3))

TIP 2: by convention, the VarStore object is placed in an object’s var slot. You can add a VarStore object to a custom object (e.g. a Dallinger Node) as follows:

from dallinger.models import Node
from psynet.field import VarStore

class CustomNode(Node):
    __mapper_args__ = {"polymorphic_identity": "custom_node"}

    @property
    def var(self):
        return VarStore(self)

TIP 3: avoid storing large objects here on account of the performance cost of converting to and from JSON.