ffmpeg-python compression code not compressing. no error message just not changing file size

Question

I'm really lost, I'm not sure what the issue is. The file is processing as the program takes longer to run the longer the video is, but it just does nothing. I don't think the compressed file is being output for some reason, and I cant figure it out. Help appreciated, but it may be hard as there is no error message of any kind.

##import section:this part is where I import all of the modules I will use
import  tkinter
import shutil
from tkinter import filedialog
import os
import random
import ffmpeg


def fileSelect():                                                                           #start of fileSelect function
    global startingLocation                                                                 #declares startingLocation as global variable
    global originalName                                                                     #declares originalName as global variable
    global fileType                                                                         #declares fileType as global variable
    startingLocation = filedialog.askopenfilename(initialdir="/", title="Select file",      #tkinter function that opens file explorer, lets user select file saves the file path as a variable
                    filetypes=(("video files", "*.mp4"),("images", "*.jpg*")))
    originalName = os.path.basename(startingLocation)                                       #os function that gets the actaul file name from the path string
    print (originalName)                                                                    #print statement to check if originalName has been found
    fileType = startingLocation.split('.')                                                  #splits original name where any full stop in found and saves array as variable
    fileType = fileType[-1]                                                                 #changes variable to have the str value of the final item in the array; the file type
    fileType = '.' + fileType                                                               #adds fullstop to the start of the file type so i dont have to repeatedly do it
    print (fileType)                                                                        #print statement to check file type is found correctly

def outputSelect():                                                                         #start of outputSelect function
     global outputLocation                                                                  #declares outputLocation as global variable
     outputLocation = filedialog.askdirectory(initialdir="/", title="Select folder")        #tkinter function that opens file explorer, lets the user select of folder as saves the folder path as a variable

def fileNewName():                                                                          #start of fileNewName function
    global customName                                                                       #declares customName as global variable
    customName = input("Enter the end name of your file ")                                  #simple code assigning user input to the custom name vairable
    if customName and customName.strip():                                                   #if statement to check if user name is blank
        customName = customName + fileType                                                  #add the fileType onto the end of the custom name
    
    else:                                                                                   #else
        list = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '1','2', '3', '4', '5', '6', '7', '8', '9','0']
        customGen = ''                                                                      #declares customGen as a string (36 characters)
        for x in range (0,8):                                                               #loop for 8 to make custom name 8 letters long
            x = random.randint(0,35)                                                        #selects a random number the length of the array
            customGen = customGen + list[x]                                                 #adds random character from list to the string
        customName = customGen + fileType                                                   #if user name blank, changes variable to custom name
    print(customName)                                                                       #print statement to check the custom name

def compress():                                                                             #start of compress function
    fileSelect()                                                                            #calls the fileSelect function
    outputSelect()                                                                          #calls the outputSelect function
    fileNewName()                                                                           #calls the fileNewName function
    global src                                                                              #declares src as a global variable
    global dst                                                                              #declares dst as a global variable
    src = startingLocation                                                                  #assigns startingLocation str as src, so the shutil module is able to use it in a cleaner way
    dst = outputLocation                                                                    #assigns outputLocation dst as src, so the shutil module is able to use it in a cleaner way
    shutil.copy(src, dst)                                                                   #shutil command that copies the file from src to dst
    src = outputLocation + '/' + originalName                                               #reassigns src as the location of the file copy
    dst = outputLocation + '/' + customName                                                 #reassigns dst as the location of the file copy but with a new name
    shutil.move(src,dst)                                                                    #moves and renames the file
    print(dst)


def compressVideo(videoFullPath, videoFileName, targetSize):
    minAudioBitrate = 32000
    maxAudioBitrate = 256000

    probe = ffmpeg.probe(videoFullPath)
    duration = float(probe['format']['duration'])
    audioBitrate = float(next((s for s in probe['streams'] if s['codec_type'] == 'audio'), None)['bit_rate'])
    targetTotalBitrate = (targetSize * 1024 * 8) / (1.073741824 * duration)

    if 10 * audioBitrate > targetTotalBitrate:
        audioBitrate = targetTotalBitrate / 10
        if audioBitrate < minAudioBitrate < targetTotalBitrate:
            audioBitrate = minAudioBitrate
        elif audioBitrate > maxAudioBitrate:
            audioBitrate = maxAudioBitrate
    videoBitrate = targetTotalBitrate - audioBitrate

    i = ffmpeg.input(videoFullPath)
    ffmpeg.output(i,'NUL',
                  **{'c:v': 'libx264', 'b:v': videoBitrate, 'pass': 1, 'f': 'null'}
                  ).overwrite_output().run()
    ffmpeg.output(i, videoFileName,
                  **{'c:v': 'libx264', 'b:v': videoBitrate, 'pass': 2, 'c:a': 'aac', 'b:a': audioBitrate, 'f' :'mp4'}
                  ).overwrite_output().run()

compress()
compressVideo(dst, customName + 'compressed', 50 * 1000)