Batch importing raster TIFFs into PostgreSQL using Python

I have a fairly simple script where I aim to insert roughly 30 raster TIFFs into a PostgreSQL database.

To manually import one TIFF at a time I run this command

raster2pgsql.exe -s 2263 -d -C -I -M -l 2,4,8,16 rasterpath_001.tif -F -t 100x100 dem_001 | psql -d raster_test -U postgres -p 5434

This works great

Now to the Python script

folder=r'rasterpath'
for x in os.listdir(folder):
    if x.endswith('.tif'):
        fname='dem_'+x[-7:][:3]
        pg= "raster2pgsql.exe -s 2263 -d -C -I -M -l 2,4,8,16 {0} -F -t 100x100 {1} | psql -d raster_test -U postgres -p 5434 ".format(os.path.join(folder,x),fname)
        print(pg)
        subprocess.run(pg)

I get this error

ERROR: Unable to read raster file: dem_001
ERROR: Unable to read raster file: dem_002
...

But if I run the printed output from the Python script manually into the CMD it succesfully runs.

Kind of confused on what is going wrong here.

Using Python 3.7

#!/bin/bash
PATH=/path/to/dest/
OPTIONS="-s 2263 -d -C -I -M -l 2,4,8,16 -F -t 100x100" 
CMD_PIPE="psql -d raster_test -U postgres -p 5434"
for fname in dem_001 dem_002;
do raster2pgsql $OPTIONS *.tif $fname | $CMD_PIPE;
done

:: windows (not tested)
:: FOR %%A IN (list) DO command parameters
%%OPTIONS="-s 2263 -d -C -I -M -l 2,4,8,16 -F -t 100x100"
%%TMP_FILE='tmpfile.sql'
FOR %%fname IN (dem_001 dem_002)
DO (raster2pgsql.exe %%OPTIONS *.tif %%fname >> %%TMP_FILE)