SPARQLWrapper: how to interpolate python variables in query

[Robert Alexander]

Dear friends,

I am a beginner so please bear with me.

I find the """ """ style of writing the queries in my code very readable but I am not able to introduce a variable in it.

For example:

sparql.setQuery("""

select distinct ?id ?eurovoc

where {

?atto a ocd:aic .

?atto dc:identifier ?id .

?atto ocd:startDate ?datapres .

?atto <http://purl.org/dc/terms/subject> ?eurovoc .

FILTER(REGEX(?datapres,'2021\\\\d{4}'))

}

""")

in the above query I would like 2021 to be instantiated by a "year" variable I previously set in the code.

Any suggestions? Thank you very much and happy 2022

Robert

[Marijane White]

Hello Robert,

 

You’ll need to use one of Python’s string formatting features, which provide functionality for inserting variables into strings. The current state of the art are f-strings, but note that you will have to double all the curly braces in your query string if you use them because f-strings use curly braces to denote variable names.

 

Here’s a nice article from Real Python about all three ways to format strings in Python, and their various pros and cons.

https://realpython.com/python-f-strings/

 

 

Marijane White, M.S.L.I.S.

Data and Research Engagement Librarian, Assistant Professor

Oregon Health & Science University Library

 

Email: whi...@ohsu.edu

ORCiD: https://orcid.org/0000-0001-5059-4132

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[Nicholas Car]

Hi Robert,

Marijane is correct! My favorite way of using variables in RDFlib SPARQL queries is to use string replace() so that I don't have to double-up {  and }, so I would do something like...

...I'll put a complete answer in if you re-post this to Stack Overflow please! That's where we like to keep all our RDFlib How-To questions! This list's just for RDFlib development.

Cheers,

Nick

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[Gunnar Aastrand Grimnes]

Using string replace isn't a great idea if you don't trust the input - re: SQL/SPARQL injection and little bobby tables: https://xkcd.com/327/

I don't think it works with SPARQLWrapper - but with the SPARQLStore you can pass your binding as RDFLib terms: 

  dbo = Namespace("http://dbpedia.org/ontology/")

  graph = Graph("SPARQLStore", identifier="http://dbpedia.org")

  graph.open("http://dbpedia.org/sparql")

  graph.bind('dbo', dbo)

  for row in graph.query('SELECT ?pop WHERE { ?city dbo:populationTotal ?pop }', initBindings={ 'city': URIRef("http://dbpedia.org/resource/Brisbane") })):

   .... do something with row ...

For mystery reasons this doesn't work with dbpedia though - it should generate the query: 

SELECT ?pop WHERE { ?city dbo:populationTotal ?pop } VALUES (?city) { ( <http://dbpedia.org/resource/Brisbane>) }

which should work but doesn't. I don't have time to figure that out now though :D 

- Gunnar

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[Robert Alexander]

Thank you all so much. I will ponder on all good advice you kindly offered. Will continue on Stackoverflow. I routinely use f strings but was dumbfounded by the concurrent use of the triple quotes :) Being a medical docyor I’m only an amateur 😀. Happy and safe 2022 to you all. Robert

Sent from my iPhone

On 8 Jan 2022, at 09:22, Gunnar Aastrand Grimnes <grom...@gmail.com> wrote:



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