Correct rtl_power output data due to frequency shift from an upconverter (like Spyverter or Ham-it-up)

shift_frequency.py

# This script takes in a csv file created by rtl_power and shifts the frequencies by CONVERTER_SHIFT Hz.
# This is needed when using rtl_power through an upconverter to correct the output frequency range in the data before being put through a heatmap generator. 

import sys, os

CONVERTER_SHIFT = -125000000 #ham-it-up
#CONVERTER_SHIFT = -120000000 #spyverter

OUT_EXTENSION = "shifted" #What extension to prepend to the actual file extension e.g. outdata.shifted.csv


#The newfilename is what we wanted to use but it already exists. Just add a number and try again.
def get_new_filename(newfilename):
    while os.access(newfilename, os.F_OK) is True:
        #Does it have a number already? Would be like filename.shifted.x.csv
        if newfilename[-5:][0].isnumeric():
            addnum = int(newfilename[-5:][0]) + 1
            n = -5
        else:
            addnum = 1
            n = -3
        newfilename = newfilename[:n] + str(addnum) + ".csv"
    return newfilename
    

# Go line-by-line and write each new line as its made. If we run into a line that is nonconforming we will probably crash or do something dumb.
#Format for the csv file is:
# date, time, Hz low, Hz high, Hz step, samples, dB, dB, dB, ...
def create_new_shifted_csv(origfilename):
    print("Shifting frequencies in file '%s'" % origfilename)
    newfilename = origfilename[:-3] + "shifted.csv"
    #Make sure we're not about to overwrite an existing file and change the name if we are. 
    if os.access(newfilename, os.F_OK):
        newfilename = get_new_filename(newfilename)
    with open(newfilename, "w") as newcsvout, open(origfilename, "r") as oldcsvin:
        curline = oldcsvin.readline()
        while curline != '':
            splitline = curline.split(", ")
            #Add frequency shift to index 2 and 3 (Hz low, Hz high)
            splitline[2] = str(CONVERTER_SHIFT + int(splitline[2]))
            splitline[3] = str(CONVERTER_SHIFT + int(splitline[3]))
            newline = ", ".join(splitline)
            newcsvout.write(newline)
            curline = oldcsvin.readline()
    print("Finished shifting and wrote to new file: '%s'\n" % newfilename)


if __name__ == "__main__": 
    if len(sys.argv) < 2:
        print("Syntax: shift_frequency.py <file1.csv> [file2.csv] ...")
        print("Adjust frequency shift amount by editing CONVERTER_SHIFT variable on line 6.")
    
    #Only accept csv files.
    filelist = [f for f in sys.argv[1:] if f[-3:].lower() == "csv"]
    for f in filelist:
        if not os.access(f, os.R_OK):
            print("Error trying to read: '%s', skipping file..." % f)
            continue
        create_new_shifted_csv(f)
    
    print("Done converting file list")

In a gist this time instead of its own repo, will see how well google indexes it.