Write and append new list parameter (without *args)

import os

def writeit(fileName,listName,functionName,localVariable, loc_name,loc_id,loc_lvl):

    var_name = lambda x:[ n for n in globals() if id(globals()[n]) == id(x) ][0]

    if ( os.stat(fileName).st_size == 0 ):
        File = open(fileName,"w")

        File.write("def "+functionName+"():\n\t"+localVariable+"."+str(var_name(listName))+" = ")
        listName.append((loc_name,loc_id,loc_lvl))

        list_str = str(listName)
        index    = list_str.index("]")
        cut_list = list_str[:index]+list_str[index+1:]
        result   = cut_list

        File.write(str(result)+"]")
        File.close()

    elif ( os.stat(fileName).st_size > 0 ):

        with open(fileName, 'rb+') as filehandle:
            filehandle.seek(-1, os.SEEK_END)
            filehandle.truncate()
            filehandle.close()

        File = open(fileName,"a")
        File.write("\n\t")
        listName.append((loc_name,loc_id,loc_lvl))

        list_str = str(listName)
        list_str = list_str.replace("[","")
        list_str = list_str.replace("]","")

        File.write(","+str(list_str)+"]")
        File.close()