Class PQLPar
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object --+
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PQLPar
- Known Subclasses:
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a representation for PQL expressions.
PQLPar objects have an attribute qualifier (None or a string), and an
attribute ranges, a list of PQLRange objects.
As a client, you will ususally construct PQLPar objects using the
fromLiteral class method; it takes a PQL literal and a name to be used
for LiteralParseErrors it may raise.
The plain PQLPar parses string ranges and does not allow steps.
Inheriting classes must override the valParser and stepParser
attributes. Both take a string and have to return a typed value or raise
a ValueError if the string does not contain a proper literal. The default
for valParser is str, the default for stepParser a function that always
raises a ValueError.
PQLPars usually support a covers(value) method that you can pass a
value having the required type; it will return whether or not value would
be picked up by the condition formulated in PQL. Some advanced PQLPars do
not support this method and will raise a ValueError if called.
Since "PQL" is totally crazy, not even the range parser is
constant. It seems string ranges were never meant to be supported, and
therefore we support RangeClass. PQLRange allows the "/"
syntax and is supposed to work for most things but strings. PQLNoRange
is just always a simple value.
Note: valParser and stepParser must not be *methods* of the class but
plain functions; since they are function-like class attributes, you will
usually have to wrap them in staticmethods
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__init__(self,
ranges,
qualifier=None,
destName=None)
x.__init__(...) initializes x; see help(type(x)) for signature |
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getSQL(self,
colName,
sqlPars,
cmpExpr=None)
returns an SQL condition expressing this PQL constraint for colName. |
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covers(self,
value)
returns true if value is within the ranges specified by the PQL
expression. |
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Inherited from object:
__delattr__,
__format__,
__getattribute__,
__hash__,
__new__,
__reduce__,
__reduce_ex__,
__setattr__,
__sizeof__,
__subclasshook__
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fromLiteral(cls,
val,
destName)
returns a parsed representation of a literal in PQL range-list
syntax. |
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Inherited from object:
__class__
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__init__(self,
ranges,
qualifier=None,
destName=None)
(Constructor)
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x.__init__(...) initializes x; see help(type(x)) for signature
- Overrides:
object.__init__
- (inherited documentation)
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__str__(self)
(Informal representation operator)
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str(x)
- Overrides:
object.__str__
- (inherited documentation)
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repr(x)
- Overrides:
object.__repr__
- (inherited documentation)
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fromLiteral(cls,
val,
destName)
Class Method
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returns a parsed representation of a literal in PQL range-list
syntax.
val is a string containing the PQL expression, destName is a name to
be used for the LiteralParseErrors the function raises when there are
syntax errors in val.
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returns a set of all values mentioned within the PQL expression.
This raises a ValueError if this is not possible (e.g., due to
non-stepped intervals).
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getSQL(self,
colName,
sqlPars,
cmpExpr=None)
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returns an SQL condition expressing this PQL constraint for
colName.
The parameters necessary are added to sqlPars.
cmpExpr can be used to override the cmpExpr argument to
PQLRange.getSQL; this is not really intended for user code, though, but
rather for subclasses of PQLPar
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returns true if value is within the ranges specified by the PQL
expression.
value must be type-true, i.e., you are responsible for converting it
into the type the range are in.
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