FHIRPath Parser & Lexer¶

FHIRPath lexer and parser components.

parser ¶

FHIRPath parser implementation using PLY (Python Lex-Yacc).

Classes:

Name	Description
`FHIRPathParser`	An LALR-parser for FHIRPath with LRU cache for parsed expressions.
`IteratorToTokenStream`	A wrapper class that converts an iterator of tokens into a token stream compatible with PLY's parser.

FHIRPathParser
Path: `fhircraft.fhir.path.parser.FHIRPathParser`
¶

FHIRPathParser(debug=False, lexer_class=None, cache_limit=1000)

An LALR-parser for FHIRPath with LRU cache for parsed expressions.

The parser uses an OrderedDict-based LRU (Least Recently Used) cache to store parsed expressions. The cache has a configurable size limit (default: 1000 expressions) to prevent unbounded memory growth. When the cache reaches its limit, the least recently used expression is evicted.

Parameters:

Name	Type	Description	Default
`debug`	`bool`	Whether to enable debug output for the parser. Defaults to False.	`False`
`lexer_class`	`type`	Custom lexer class to use. Defaults to FHIRPathLexer.	`None`
`cache_limit`	`int`	Maximum number of expressions to cache. Defaults to 1000. When the cache exceeds this limit, the least recently used expression is evicted.	`1000`

Raises:

Type	Description
`FHIRPathParsingError`	If docstrings have been removed (required by PLY).

Methods:

Name	Description
`parse`	Parse a FHIRPath expression string and return the corresponding FHIRPath object.
`is_valid`	Check if a FHIRPath expression string is valid without raising exceptions.
`parse_token_stream`	Parse a stream of tokens and return the corresponding FHIRPath object.
`p_fhirpath_term_expression`	expression : term
`p_fhirpath_invocation_expression`	expression : expression '.' invocation
`p_fhirpath_indexer_expression`	expression : expression '[' expression ']'
`p_fhirpath_multiplicative_operation`	expression : expression '*' expression
`p_fhirpath_additive_operation`	expression : expression '+' expression
`p_fhirpath_type_operation`	expression : expression IS type_specifier
`p_fhirpath_union_operation`	expression : expression '\|' expression
`p_fhirpath_equality_operation`	expression : expression EQUAL expression
`p_fhirpath_inequality_operation`	expression : expression GREATER_THAN expression
`p_fhirpath_membership_fhirpath_operation`	expression : expression IN expression
`p_fhirpath_and_operation`	expression : expression AND expression
`p_fhirpath_or_operation`	expression : expression OR expression
`p_fhirpath_implies_operation`	expression : expression IMPLIES expression
`p_fhirpath_term`	term : invocation
`p_fhirpath_parenthesized_expression`	parenthesized_expression : '(' expression ')'
`p_fhirpath_invocation`	invocation : element
`p_fhirpath_root`	root : ROOT_NODE
`p_fhirpath_element`	element : identifier
`p_fhirpath_typechoice_invocation`	type_choice : CHOICE_ELEMENT
`p_fhirpath_constant`	constant : ENVIRONMENTAL_VARIABLE
`p_fhirpath_contextual`	contextual : CONTEXTUAL_OPERATOR
`p_fhirpath_type_specifier`	type_specifier : identifier
`p_fhirpath_type_specifier_context`	type_specifier : identifier '.' identifier
`p_fhirpath_function`	function : function_name '(' arguments ')'
`p_fhirpath_type_function`	function : OFTYPE '(' type_specifier ')'
`p_fhirpath_function_name`	function_name : identifier
`p_fhirpath_function_arguments`	arguments : arguments ',' argument
`p_fhirpath_function_argument`	argument : expression
`p_fhirpath_identifier`	identifier : IDENTIFIER
`p_fhirpath_polar_literal`	literal : '+' number
`p_fhirpath_literal`	literal : number
`p_fhirpath_literal_empty`	literal : '{' '}'
`p_fhirpath_boolean`	boolean : BOOLEAN
`p_fhirpath_datetime`	datetime : DATETIME
`p_fhirpath_time`	time : TIME
`p_fhirpath_date`	date : DATE
`p_fhirpath_quantity`	quantity : number unit
`p_fhirpath_unit`	unit : STRING
`p_fhirpath_number`	number : INTEGER
`p_fhirpath_empty`	empty :

Attributes:

Name	Type	Description
`tokens`		The list of token names used by the parser. This is required by PLY.
`input_string`	`str`	The input string being parsed. Used for error reporting.
`debug`	`bool`	Whether to enable debug output for the parser.
`cache_limit`	`int`	Maximum number of expressions to cache. Oldest (least recently used) are evicted when limit is reached.
`lexer_class`	`FHIRPathLexer \| type`	The lexer class used by the parser. Defaults to FHIRPathLexer.
`lexer`	`FHIRPathLexer \| None`	The lexer instance used by the parser.
`lr_parser`	`LRParser \| None`	The LALR parser instance generated by PLY.
`cache`	`OrderedDict[str, FHIRPath]`	A cache of parsed FHIRPath expressions to avoid re-parsing the same expression. Uses LRU eviction policy.
`cache_info`	`dict`	Return cache statistics including size, limit, and stored expression strings.

tokens `class-attribute` `instance-attribute` ¶

tokens = FHIRPathLexer.tokens

The list of token names used by the parser. This is required by PLY.

input_string `instance-attribute` ¶

input_string: str

The input string being parsed. Used for error reporting.

debug `class-attribute` `instance-attribute` ¶

debug: bool = debug

Whether to enable debug output for the parser.

cache_limit `class-attribute` `instance-attribute` ¶

cache_limit: int = cache_limit

Maximum number of expressions to cache. Oldest (least recently used) are evicted when limit is reached.

lexer_class `class-attribute` `instance-attribute` ¶

lexer_class: FHIRPathLexer | type = lexer_class or FHIRPathLexer

The lexer class used by the parser. Defaults to FHIRPathLexer.

lexer `class-attribute` `instance-attribute` ¶

lexer: FHIRPathLexer | None = self.lexer_class()

The lexer instance used by the parser.

lr_parser `class-attribute` `instance-attribute` ¶

lr_parser: LRParser | None = ply.yacc.yacc(module=self, debug=self.debug, tabmodule=parsing_table_module, outputdir=output_directory, write_tables=False, start=start_symbol, errorlog=logger)

The LALR parser instance generated by PLY.

cache `class-attribute` `instance-attribute` ¶

cache: OrderedDict[str, FHIRPath] = OrderedDict()

A cache of parsed FHIRPath expressions to avoid re-parsing the same expression. Uses LRU eviction policy.

cache_info `property` ¶

cache_info: dict

Return cache statistics including size, limit, and stored expression strings.

parse ¶

parse(input_string: str) -> FHIRPath | Any

Parse a FHIRPath expression string and return the corresponding FHIRPath object.

Results are cached using an LRU policy. Cached expressions are returned immediately
without re-parsing. Accessing a cached expression updates its position in the LRU
queue to mark it as recently used.

Parameters:

Name	Type	Description	Default
`input_string`	`str`	The FHIRPath expression string to parse.	required

Returns:

Name	Type	Description
`FHIRPath`	`FHIRPath \| Any`	The parsed FHIRPath object representing the expression.

Raises:

Type	Description
`FHIRPathParsingError`	If there is a parsing error in the input string.

is_valid ¶

is_valid(input_string: str) -> bool

Check if a FHIRPath expression string is valid without raising exceptions.

Parameters:

Name	Type	Description	Default
`input_string`	`str`	The FHIRPath expression string to validate.	required

Returns:

Name	Type	Description
`bool`	`bool`	True if the expression is valid, False otherwise.

parse_token_stream ¶

parse_token_stream(token_iterator: Iterator) -> FHIRPath

Parse a stream of tokens and return the corresponding FHIRPath object.

Parameters:

Name	Type	Description	Default
`token_iterator`	`Iterator`	An iterator that yields tokens from the lexer.	required

Returns:

Name	Type	Description
`FHIRPath`	`FHIRPath`	The parsed FHIRPath object representing the expression.

p_fhirpath_term_expression ¶

p_fhirpath_term_expression(p)

expression : term

p_fhirpath_invocation_expression ¶

p_fhirpath_invocation_expression(p)

expression : expression '.' invocation

p_fhirpath_indexer_expression ¶

p_fhirpath_indexer_expression(p)

expression : expression '[' expression ']'

p_fhirpath_multiplicative_operation ¶

p_fhirpath_multiplicative_operation(p)

expression : expression '*' expression | expression '/' expression | expression DIV expression | expression MOD expression

p_fhirpath_additive_operation ¶

p_fhirpath_additive_operation(p)

expression : expression '+' expression | expression '-' expression | expression '&' expression

p_fhirpath_type_operation ¶

p_fhirpath_type_operation(p)

expression : expression IS type_specifier | expression AS type_specifier

p_fhirpath_union_operation ¶

p_fhirpath_union_operation(p)

expression : expression '|' expression

p_fhirpath_equality_operation ¶

p_fhirpath_equality_operation(p)

expression : expression EQUAL expression | expression EQUIVALENT expression | expression NOT_EQUAL expression | expression NOT_EQUIVALENT expression

p_fhirpath_inequality_operation ¶

p_fhirpath_inequality_operation(p)

expression : expression GREATER_THAN expression | expression GREATER_EQUAL_THAN expression | expression LESS_THAN expression | expression LESS_EQUAL_THAN expression

p_fhirpath_membership_fhirpath_operation ¶

p_fhirpath_membership_fhirpath_operation(p)

expression : expression IN expression | expression CONTAINS expression

p_fhirpath_and_operation ¶

p_fhirpath_and_operation(p)

expression : expression AND expression

p_fhirpath_or_operation ¶

p_fhirpath_or_operation(p)

expression : expression OR expression | expression XOR expression

p_fhirpath_implies_operation ¶

p_fhirpath_implies_operation(p)

expression : expression IMPLIES expression

p_fhirpath_term ¶

p_fhirpath_term(p)

term : invocation | literal | constant | parenthesized_expression

p_fhirpath_parenthesized_expression ¶

p_fhirpath_parenthesized_expression(p)

parenthesized_expression : '(' expression ')'

p_fhirpath_invocation ¶

p_fhirpath_invocation(p)

invocation : element | root | type_choice | function | contextual

p_fhirpath_root ¶

p_fhirpath_root(p)

root : ROOT_NODE

p_fhirpath_element ¶

p_fhirpath_element(p)

element : identifier

p_fhirpath_typechoice_invocation ¶

p_fhirpath_typechoice_invocation(p)

type_choice : CHOICE_ELEMENT

p_fhirpath_constant ¶

p_fhirpath_constant(p)

constant : ENVIRONMENTAL_VARIABLE

p_fhirpath_contextual ¶

p_fhirpath_contextual(p)

contextual : CONTEXTUAL_OPERATOR

p_fhirpath_type_specifier ¶

p_fhirpath_type_specifier(p)

type_specifier : identifier | ROOT_NODE

p_fhirpath_type_specifier_context ¶

p_fhirpath_type_specifier_context(p)

identifier '.' identifier

| identifier '.' ROOT_NODE

p_fhirpath_function ¶

p_fhirpath_function(p)

function : function_name '(' arguments ')'

p_fhirpath_type_function ¶

p_fhirpath_type_function(p)

function : OFTYPE '(' type_specifier ')' | IS '(' type_specifier ')' | AS '(' type_specifier ')'

p_fhirpath_function_name ¶

p_fhirpath_function_name(p)

function_name : identifier | CONTAINS | IN

p_fhirpath_function_arguments ¶

p_fhirpath_function_arguments(p)

arguments ',' argument

| argument

p_fhirpath_function_argument ¶

p_fhirpath_function_argument(p)

argument : expression | empty

p_fhirpath_identifier ¶

p_fhirpath_identifier(p)

identifier : IDENTIFIER

p_fhirpath_polar_literal ¶

p_fhirpath_polar_literal(p)

'+' number

| '-' number

p_fhirpath_literal ¶

p_fhirpath_literal(p)

p_fhirpath_literal_empty ¶

p_fhirpath_literal_empty(p)

literal : '{' '}'

p_fhirpath_boolean ¶

p_fhirpath_boolean(p)

boolean : BOOLEAN

p_fhirpath_datetime ¶

p_fhirpath_datetime(p)

datetime : DATETIME

p_fhirpath_time ¶

p_fhirpath_time(p)

time : TIME

p_fhirpath_date ¶

p_fhirpath_date(p)

date : DATE

p_fhirpath_quantity ¶

p_fhirpath_quantity(p)

quantity : number unit

p_fhirpath_unit ¶

p_fhirpath_unit(p)

unit : STRING | CALENDAR_DURATION

p_fhirpath_number ¶

p_fhirpath_number(p)

number : INTEGER | DECIMAL

p_fhirpath_empty ¶

p_fhirpath_empty(p)

empty :

IteratorToTokenStream
Path: `fhircraft.fhir.path.parser.IteratorToTokenStream`
¶

IteratorToTokenStream(iterator: Iterator)

A wrapper class that converts an iterator of tokens into a token stream compatible with PLY's parser.

Methods:

Name	Description
`token`	Retrieve the next token from the iterator.

token ¶

token()

Retrieve the next token from the iterator.

lexer ¶

Classes:

Name	Description
`FHIRPathLexer`	A Lexical analyzer for JsonPath.

FHIRPathLexer
Path: `fhircraft.fhir.path.lexer.FHIRPathLexer`
¶

FHIRPathLexer(debug=False)

A Lexical analyzer for JsonPath.

Methods:

Name	Description
`tokenize`	Maps a string to an iterator over tokens. In other words: [char] -> [token]
`t_ignore_WHITESPACE`	[\s]
`t_ignore_COMMENT`	\/([\s\S]?)\/\|\/\/(.)
`t_CHOICE_ELEMENT`	(?:`[a-zA-Z][a-zA-Z0-9-][^`][x]`)\|(?:(?:\|[a-zA-Z])[a-zA-Z0-9][x])
`t_ENVIRONMENTAL_VARIABLE`	(?:\%[a-zA-Z][a-zA-Z0-9-]\|\%`[a-zA-Z][a-zA-Z0-9-][^`]`)
`t_CONTEXTUAL_OPERATOR`	$(\w*)?
`t_DATETIME`	@\d{4}(?:-\d{2}(?:-\d{2})?)?T(?:\d{2}(?::\d{2}(?::\d{2}(?:.\d{3}(?:[+\|-]\d{2}(?::\d{2})?)?)?)?)?)?
`t_DATE`	@\d{4}(?:-\d{2}(?:-\d{2})?)?
`t_TIME`	\@T\d{2}(?::\d{2}(?::\d{2}(?:.\d{3}(?:[+\|-]\d{2}(?::\d{2})?)?)?)?)?
`t_NUMBER`	\d+(.\d+)?
`t_STRING`	\'((?:[^\'\]\|\.)*)\'
`t_IDENTIFIER`	(?:`[a-zA-Z][a-zA-Z0-9-][^`]`)\|(?:(?:\|[a-zA-Z])[a-zA-Z0-9])
`t_NOT_EQUAL`	!=
`t_NOT_EQUIVALENT`	!~
`t_GREATER_EQUAL_THAN`	=
`t_LESS_EQUAL_THAN`	<=
`t_LESS_THAN`	<
`t_GREATER_THAN`
`t_EQUAL`	=
`t_EQUIVALENT`	~
`t_error_invalid_function`	[a-zA-Z][a-zA-Z_0-9]$(?:.)?$
`t_error_doublequote_string`	\"([^\"]*)?\"

tokenize ¶

tokenize(string)

Maps a string to an iterator over tokens. In other words: [char] -> [token]

t_ignore_WHITESPACE ¶

t_ignore_WHITESPACE(t)

[\s]

t_ignore_COMMENT ¶

t_ignore_COMMENT(t)

\/*([\s\S]?)*\/|\/\/(.)

t_CHOICE_ELEMENT ¶

t_CHOICE_ELEMENT(t)

(?:`[a-zA-Z][a-zA-Z0-9-][^`][x]`)|(?:(?:|[a-zA-Z])[a-zA-Z0-9][x])

t_ENVIRONMENTAL_VARIABLE ¶

t_ENVIRONMENTAL_VARIABLE(t)

(?:\%[a-zA-Z][a-zA-Z0-9-]|\%`[a-zA-Z][a-zA-Z0-9-][^`]`)

t_CONTEXTUAL_OPERATOR ¶

t_CONTEXTUAL_OPERATOR(t)

$(\w*)?

t_DATETIME ¶

t_DATETIME(t)

@\d{4}(?:-\d{2}(?:-\d{2})?)?T(?:\d{2}(?::\d{2}(?::\d{2}(?:.\d{3}(?:[+|-]\d{2}(?::\d{2})?)?)?)?)?)?

t_DATE ¶

t_DATE(t)

@\d{4}(?:-\d{2}(?:-\d{2})?)?

t_TIME ¶

t_TIME(t)

\@T\d{2}(?::\d{2}(?::\d{2}(?:.\d{3}(?:[+|-]\d{2}(?::\d{2})?)?)?)?)?

t_NUMBER ¶

t_NUMBER(t)

\d+(.\d+)?

t_STRING ¶

t_STRING(t)

\'((?:[^\'\]|\.)*)\'

t_IDENTIFIER ¶

t_IDENTIFIER(t)

(?:`[a-zA-Z][a-zA-Z0-9-][^`]`)|(?:(?:|[a-zA-Z])[a-zA-Z0-9])

t_NOT_EQUAL ¶

t_NOT_EQUAL(t)

!=

t_NOT_EQUIVALENT ¶

t_NOT_EQUIVALENT(t)

!~

t_GREATER_EQUAL_THAN ¶

t_GREATER_EQUAL_THAN(t)

=

t_LESS_EQUAL_THAN ¶

t_LESS_EQUAL_THAN(t)

<=

t_LESS_THAN ¶

t_LESS_THAN(t)

<

t_GREATER_THAN ¶

t_GREATER_THAN(t)

t_EQUAL ¶

t_EQUAL(t)

=

t_EQUIVALENT ¶

t_EQUIVALENT(t)

~

t_error_invalid_function ¶

t_error_invalid_function(t)

[a-zA-Z][a-zA-Z_0-9]*$(?:.*)?$

t_error_doublequote_string ¶

t_error_doublequote_string(t)

\"([^\"]*)?\"

FHIRPath Parser & Lexer¶

parser ¶

FHIRPathParser Path: fhircraft.fhir.path.parser.FHIRPathParser ¶

tokens class-attribute instance-attribute ¶

input_string instance-attribute ¶

debug class-attribute instance-attribute ¶

cache_limit class-attribute instance-attribute ¶

lexer_class class-attribute instance-attribute ¶

lexer class-attribute instance-attribute ¶

lr_parser class-attribute instance-attribute ¶

cache class-attribute instance-attribute ¶

cache_info property ¶

parse ¶

is_valid ¶

parse_token_stream ¶

p_fhirpath_term_expression ¶

p_fhirpath_invocation_expression ¶

p_fhirpath_indexer_expression ¶

p_fhirpath_multiplicative_operation ¶

p_fhirpath_additive_operation ¶

p_fhirpath_type_operation ¶

p_fhirpath_union_operation ¶

p_fhirpath_equality_operation ¶

p_fhirpath_inequality_operation ¶

p_fhirpath_membership_fhirpath_operation ¶

p_fhirpath_and_operation ¶

p_fhirpath_or_operation ¶

p_fhirpath_implies_operation ¶

p_fhirpath_term ¶

p_fhirpath_parenthesized_expression ¶

p_fhirpath_invocation ¶

p_fhirpath_root ¶

p_fhirpath_element ¶

p_fhirpath_typechoice_invocation ¶

p_fhirpath_constant ¶

p_fhirpath_contextual ¶

p_fhirpath_type_specifier ¶

p_fhirpath_type_specifier_context ¶

p_fhirpath_function ¶

p_fhirpath_type_function ¶

p_fhirpath_function_name ¶

p_fhirpath_function_arguments ¶

p_fhirpath_function_argument ¶

p_fhirpath_identifier ¶

p_fhirpath_polar_literal ¶

p_fhirpath_literal ¶

p_fhirpath_literal_empty ¶

p_fhirpath_boolean ¶

p_fhirpath_datetime ¶

p_fhirpath_time ¶

p_fhirpath_date ¶

p_fhirpath_quantity ¶

p_fhirpath_unit ¶

p_fhirpath_number ¶

p_fhirpath_empty ¶

IteratorToTokenStream Path: fhircraft.fhir.path.parser.IteratorToTokenStream ¶

token ¶

lexer ¶

FHIRPathLexer Path: fhircraft.fhir.path.lexer.FHIRPathLexer ¶

tokenize ¶

t_ignore_WHITESPACE ¶

t_ignore_COMMENT ¶

t_CHOICE_ELEMENT ¶

t_ENVIRONMENTAL_VARIABLE ¶

t_CONTEXTUAL_OPERATOR ¶

t_DATETIME ¶

t_DATE ¶

t_TIME ¶

t_NUMBER ¶

t_STRING ¶

t_IDENTIFIER ¶

t_NOT_EQUAL ¶

t_NOT_EQUIVALENT ¶

t_GREATER_EQUAL_THAN ¶

t_LESS_EQUAL_THAN ¶

t_LESS_THAN ¶

t_GREATER_THAN ¶

t_EQUAL ¶

t_EQUIVALENT ¶

t_error_invalid_function ¶

FHIRPathParser
Path: `fhircraft.fhir.path.parser.FHIRPathParser`
¶

tokens `class-attribute` `instance-attribute` ¶

input_string `instance-attribute` ¶

debug `class-attribute` `instance-attribute` ¶

cache_limit `class-attribute` `instance-attribute` ¶

lexer_class `class-attribute` `instance-attribute` ¶

lexer `class-attribute` `instance-attribute` ¶

lr_parser `class-attribute` `instance-attribute` ¶

cache `class-attribute` `instance-attribute` ¶

cache_info `property` ¶

IteratorToTokenStream
Path: `fhircraft.fhir.path.parser.IteratorToTokenStream`
¶

FHIRPathLexer
Path: `fhircraft.fhir.path.lexer.FHIRPathLexer`
¶