TI84 Varable File Maker

import sys

class Var_struct:
    def __init__(self,name,vt):
        self.header = [0x2A, 0x2A, 0x54, 0x49, 0x38, 0x33, 0x46, 0x2A,
                         #**TI83F*
                         0x1A, 0x0A, 0x00,
                         #signature
                         0x41, 0x70, 0x70, 0x56, 0x61, 0x72, 0x69, 0x61,
                         #comment area
                         0x62, 0x6c, 0x65, 0x20, 0x66, 0x69, 0x6c, 0x65,
                         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                         0x00, 0x00,
                         0x00, 0x00]
                             #data size
        self.varheader = [0x0D, 0x00,
                            0x00, 0x00,
                            #length of variable in bytes
                            vt,
                            #variable type ID. 0x15 is for appvar, 0x06 is for locked prgm
                            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                            #variable name (max 8 characters)
                            0x00,
                            #version
                            0x80,
                            #flag. 80h for archived variable. 00h otherwise
                            0x00, 0x00,
                            #length of variable in bytes (copy)
                            0x00, 0x00]
                            #length of variable in bytes (another copy...)
        self.checksum = -1
        if len(name)>8:
            self.name = name[0:7]
        elif len(name)==8:
            self.name = name
        else:
            self.name = name + "\x00"*(8-len(name))

        for i in range(8):
            self.varheader[i+5]=ord(self.name[i])

    def update(self,data=[]):
        if len(data)>0xFFEC:
            print("Error: Converted data too large!")
            return
        self.header[53]=(len(data)+19)%256
        self.header[54]=(len(data)+19)//256
        dl=len(data)
        self.varheader[2]=(dl+2)%256
        self.varheader[3]=(dl+2)//256
        self.varheader[15]=(dl+2)%256
        self.varheader[16]=(dl+2)//256
        self.varheader[17]=dl%256
        self.varheader[18]=dl//256
        self.data = self.header + self.varheader + data + [0,0]
        self.checksum=sum(self.varheader)+sum(data)
        self.data[-2]=self.checksum%256
        self.data[-1]=self.checksum//256
        for i in range(len(self.data)):
            self.data[i]%=256

    def write(self,file):
        try:
            with open(file,"wb") as f:
                f.write(bytes(self.data))
            return True
        except:
            print("Something went wrong writing!")
            return False


if __name__=='__main__':
    try:
        file_name = sys.argv[1]
    except:
        file_name = input("File to convert?")
    try:
        with open(file_name,"rb") as f:
            data_in = list(f.read())
    except:
        print("Error: File does not exist!")
        exit()

    try:
        calc_name = sys.argv[4]
    except:
        calc_name = input("Name on calc?")

    try:
        vartype = str(sys.argv[3]).lower()
    except:
        vartype = input("variable type?")

    try:
        vartype = int(vartype)%256
    except:
        if "prot" in vartype:
            vartype=6
        elif "prgm" in vartype:
            vartype=5
        elif "appvar" in vartype or "avar" in vartype:
            vartype=21
        else:
            print("""Error: invalid variable type!
defaulting to locked program...""")
            vartype=6

    calc_var = Var_struct(calc_name,vartype)
    calc_var.update(data_in)
    try:
        comp_name = sys.argv[2]
    except:
        comp_name = input("File name?")

    calc_var.write(comp_name)