284 lines
8.7 KiB
ReStructuredText
284 lines
8.7 KiB
ReStructuredText
.. _ref-pyson:
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.. module:: trytond.pyson
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=====
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PYSON
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=====
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PYSON is the PYthon Statement and Object Notation.
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There is also a more :ref:`practical introduction into
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PYSON statements <topics-pyson>`.
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.. class:: PYSON
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Base class of any PYSON statement. It is never used directly.
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Instance methods:
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.. method:: PYSON.pyson()
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Method that returns the internal dictionary representation of the
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statement.
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.. method:: PYSON.types()
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Method that returns a set of all possible types which the statement
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can become when evaluated.
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.. classmethod:: PYSON.eval(dct, context)
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Method which returns the evaluation of the statement given in
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``dct`` within the ``context``. ``dct`` contains a
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dictionary which is the internal representation of a PYSON
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statement. ``context`` contains a dictionary with contextual
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values.
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Encoder and Decoder
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===================
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.. class:: PYSONEncoder()
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Encoder for PYSON statements into string representations.
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Instance method:
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.. method:: PYSONEncoder.encode(object)
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Returns a string representation of a given PYSON statement.
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``object`` contains a PYSON statement.
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.. class:: PYSONDecoder([context[, noeval]])
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Decoder for string into the evaluated or not PYSON statement.
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Instance method:
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.. method:: PYSONDecoder.decode(object)
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Returns a PYSON statement evaluated or not of a given string.
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``object`` contains a string.
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Statements
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==========
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The following statements can be used in :class:`PYSON`.
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.. class:: Eval(value[, default])
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An :class:`Eval()` object represents the PYSON ``Eval()``
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statement for evaluations. When evaluated, it returns the
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value of the statement named by ``value``, if defined in the
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evaluation context, otherwise the ``default`` value (empty
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string by default).
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.. note::
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The default value determines the type of the statement.
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..
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.. note::
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If the ``value`` includes dots the value will be dereferenced. For
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example::
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Eval('_parent_sale.number')
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The ``number`` value of the ``_parent_sale`` key of the evaluation context
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will be returned.
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..
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.. class:: Not(value)
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A :class:`Not` object represents the PYSON ``Not()``
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statement for logical negations. When evaluated, returns
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the boolean negation of the value of the statement named by
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``value``, if defined in the evaluation context. Returns an
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instance of itself.
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.. class:: Bool(value)
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A :class:`Bool` object represents the PYSON ``Bool()``
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statement for boolean evaluations. Returns the boolean
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representation of the value of the statement named by
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``value``.
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.. class:: And(\*statements)
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An :class:`And` object represents the PYSON ``And()``
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statement for logical *and* operations. Returns the result of
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the logical conjunction of two or more values named by the
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statements in the ``statements`` tuple.
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.. class:: Or(\*statements)
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An :class:`Or` object represents the PYSON ``Or()``
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statement for logical *or* operations. Returns the result of
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the logical disjunction of two or more values named by the
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statements in the ``statements`` tuple.
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.. class:: Equal(statement1, statement2)
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An :class:`Equal` object represents the PYSON ``Equal()``
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statement for equation comparisons. Returns true when a value of
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a statement named by ``statement1`` and the value of a statement
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named by ``statement2`` are equal, otherwise returns false.
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.. class:: Greater(statement1, statement2[, equal])
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A :class:`Greater` object represents the PYSON ``Greater()``
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statement for *greater-than* comparisons. Returns true when the value
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of the statement named by ``statement1`` is strictly greater than the
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value of the statement named by ``statement2``, otherwise
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returns false. Is the value of the variable named by ``equal`` is
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true, then returns also true when both values of statements named by
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``statement1`` and ``statement2`` are equal. In this case
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:class:`Greater` works as a *greater-than or equal* operator.
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.. note:: ``None`` value is replaced by ``0`` for the comparison.
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.. class:: Less(statement1, statement2[, equal])
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A :class:`Less` object represents the PYSON ``Less()``
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statement for *less-than* comparisons. Returns true when the value
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of the statement named by ``statement1`` is strictly less than the
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value of the statement named by ``statement2``, otherwise
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returns false. Is the value of the variable named ``equal`` is true,
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then returns also true when both values of the statements named by
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``statement1`` and ``statement2`` are equal. In this case
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:class:`Less` works as a *less-than or equal* operator.
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.. note:: ``None`` value is replaced by ``0`` for the comparison.
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.. class:: If(condition, then_statement, else_statement)
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An :class:`If` object represents the PYSON ``If()``
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statement for conditional flow control operations. Returns the
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value of the statement named by ``then_statement`` when the value
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of the statement named by ``condition`` evaluates true.
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Otherwise returns the value of the statement named by
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``else_statement``.
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.. class:: Get(obj, key[, default])
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A :class:`Get` object represents the PYSON ``Get()``
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statement for dictionary look-up operations and evaluation.
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Look up and returns the value of a key named by ``key`` in an
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object named by ``obj`` if defined.
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Otherwise returns the value of the variable named by ``default``.
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.. class:: In(key, obj)
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An :class:`In` object represents the PYSON ``In()``
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statement for look-up dictionary or integer objects. Returns true when
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a list (or dictionary) object named by ``obj`` contains the value of
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the variable (or key) named by ``key``. Otherwise returns false.
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.. class:: Date([year[, month[, day[, delta_years[, delta_month[, delta_days[, start]]]]]]])
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A :class:`Date` object represents the PYSON ``Date()`` statement for date
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related conversions and basic calculations.
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Returns a date object which represents the values of arguments named by the
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*variables* explained below.
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Missing values of arguments named by ``year`` or ``month`` or ``day`` take
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their defaults from ``start`` or the actual date. When values of arguments
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named by ``delta_*`` are given, they are added to the values of the appropriate
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arguments in a date and time preserving manner.
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Arguments:
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``year``
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Contains a PYSON statement of type int or long.
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``month``
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Contains a PYSON statement of type int or long.
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``day``
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Contains a PYSON statement of type int or long.
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``delta_years``
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Contains a PYSON statement of type int or long.
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``delta_month``
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Contains a PYSON statement of type int or long.
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``delta_days``
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Contains a PYSON statement of type int or long.
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``start``
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Contains a PYSON statement of type date.
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.. class:: DateTime([year[, month[, day[, hour[, minute[, second[, microsecond[, delta_years[, delta_months[, delta_days[, delta_hours[, delta_minutes[, delta_seconds[, delta_microseconds[, start]]]]]]]]]]]]]]])
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A :class:`DateTime` object represents the PYSON ``Date()`` statement for date
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and time related conversions and calculations.
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Returns a date time object which represents the values of variables named by
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the *arguments* explained below.
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Missing values of arguments named by ``year``, ``month``, ``day``, ``hour``,
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``minute``, ``second``, ``microseconds`` take their defaults from ``start`` or
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the actual date and time in `UTC`_.
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When values of arguments named by ``delta_*`` are given, these are added to
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the appropriate attributes in a date and time preserving manner.
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.. _`UTC`: https://en.wikipedia.org/wiki/Coordinated_Universal_Time
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Arguments:
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``year``
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Contains a PYSON statement of type int or long.
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``month``
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Contains a PYSON statement of type int or long.
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``day``
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Contains a PYSON statement of type int or long.
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``hour``
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Contains a PYSON statement of type int or long.
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``minute``
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Contains a PYSON statement of type int or long.
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``second``
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Contains a PYSON statement of type int or long.
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``microsecond``
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Contains a PYSON statement of type int or long.
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``delta_years``
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Contains a PYSON statement of type int or long.
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``delta_month``
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Contains a PYSON statement of type int or long.
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``delta_days``
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Contains a PYSON statement of type int or long.
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``delta_hours``
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Contains a PYSON statement of type int or long.
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``delta_minutes``
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Contains a PYSON statement of type int or long.
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``delta_seconds``
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Contains a PYSON statement of type int or long.
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``delta_microseconds``
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Contains a PYSON statement of type int or long.
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``start``
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Contains a PYSON statement of type datetime.
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.. class:: Len(value)
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A :class:`Len` object represents the PYSON ``Len()`` statement for length of a
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dictionary, list or string. Returns the number of items in ``value``.
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.. class:: Id(module, fs_id)
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An :class:`Id` object represents the PYSON ``Id()`` statement for filesystem id
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evaluations. When converted into the internal dictionary, it returns the
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database id stored in ``ir.model.data``.
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