Python itertools tactic to fetch all from a paginated API finding all elements which match an arbitrary predicate

findSomeItemsByPredicate.py

import itertools
from typing import Callable

def findSomeItemsByPredicate(
  someApi: SomeApi,
  predicate: Callable[[Something],Something] ) -> Union[None, list[Something]:
  
  def getOnePage( pageIndex: int ):
  
    # fetch the requested page of Something items, if any
    return findItemsPaged( someApi, pageIndex= pageIndex, pageSize= 20 )
    
  # request page after page of content until no more pages are available - without having to know
  # the total number of pages available on the service
  
  return list( filter( predicate, itertools.chain.from_iterable( intertools.takewhile( lambda x: x, map( getOnePage, itertools.count(1) ) ) ) ) )
                                                        
# call like this (here the predicate is the always true existence check)
findSomeItemsByPredicate( myJiraApi, lambda x: x)

This streams page after page from the API service, stopping once the method which fetches a page at a time returns an empty set.

As those pages arrive, they are filtered to match the provided predicate expression and gathered into a growing list of predicate-matching Somethings.