Python code for downloading and merging pdf files in a loop results in a 1KB endfile

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Hello everyone.
I have a website that I need to get ~1000 pdfs from. The pdfs are differed by a four digit number between 1101-2300, like
https://intvd.gib.gov.tr/2014_Emlak_Arsa/EmlakServlet?tip=9&ilKodu=3&ilceKodu=1101
Some of the numbers between the range are not assigned to a pdf though, so I needed something that would
1-) dowload all the pdfs
2-) delete the pdfs that are 1KB (these are non-assigned ones)
3-) merge all the pdf files into one pdf file
There were answers to each of these steps but not together, so I looked at those and made something. In the end though, all I get is a 1 KB pdf file called merged_full.pdf
What am I doing wrong?
Cheers

What I have tried:

import urllib.request
import os
from PyPDF2 import PdfFileReader, PdfFileMerger

os.chdir('the_directory')

mylist=(list(range(1101,2500)))

for i in mylist:
    def download_file(download_url):
        web_file = urllib.request.urlopen('https://intvd.gib.gov.tr/2014_Emlak_Arsa/EmlakServlet?tip=9&ilKodu=3&ilceKodu=%d'%(i),'%d.pdf'%(i))
        local_file = open('%d.pdf'%(i), 'wb')
        local_file.write(web_file.read())
        web_file.close()
        local_file.close()
        filesize = os.path.getsize('%d.pdf'%(i))
        if filesize<1024:
                os.remove('%d.pdf'%(i))
        del filesize

files_dir = "the_directory"
pdf_files = [f for f in os.listdir(files_dir) if f.endswith("pdf")]
merger = PdfFileMerger()

for filename in pdf_files:
    merger.append(PdfFileReader(os.path.join(files_dir, filename), "rb"))

merger.write(os.path.join(files_dir, "merged_full.pdf"))