gnu parallel with no argument script

Question

I have 4 cores, and 4 python script files preprocess0.py, preprocess1.py, preprocess2.py, preprocess3.py. I would like to run these 4 processes in parallel using GNU parallel. I do not have input files. The input file is hardcoded inside each *.py file (it's read only, so it's ok). I would like to output the results to a file0.csv ... file3.csv files. This is as far as I've come:

parallel -j4 --progress python preprocess*.py ::: '>' ./file{}.csv

But it just stays there without writing anything, as if waiting for some input.

Answer 1

The syntax is:

parallel -j4 --progress 'python {} > ./file{}.csv' ::: preprocess*.py

That would create files called filepreprocess1.py.csv... You could use

parallel -j4 --progress 'python {} > ./file{#}.csv' ::: preprocess*.py

instead to use the job number instead and get some file1.csv... files. Or if you want to extract the number for the file names:

parallel -j4 --progress 'python {} > ./file{=s/[^\d]//g=}.csv' ::: preprocess*.py