[Tutor] Fwd: Re: Argparse Error

[Alan Gauld]

Forwarding to list since I seem to have messed up the address last time...

-------- Forwarded Message --------
Subject: 	Re: [Tutor] Argparse Error
Date: 	Sun, 12 Aug 2018 23:44:04 +0100
From: 	Alan Gauld <alan.gauld at yahoo.co.uk>
Reply-To: 	tutor <tutor at python.org>
To: 	Nathan Johnson <nathanj9715 at gmail.com>



On 12/08/18 19:58, Nathan Johnson wrote:
> Here is the full script that was provided, but I don't know what else
> I'm supposed to do with it except save it in the folder on my D:
> drive, and run in in the cmd prompt like you said.
>

OK, It seems as if there are some other arguments that you need
to provide. The one causing the issue here is fileout - ie the output
filename.

Now, its not clear what else needs to be specified, you probably
should ask the author. We are not really best qualified to decipher
another coders code!

But it looks like values for interval, shift and skip are required
too - although I've no idea what they mean!

What the code does tell us are the options you need to use,
so the command should look like:


python D:\Python\bytsh.py -o output.mp4 -i ??? -s ??? -k ???
D:\Video\test.mp4

Where you will need to figure out what kind of values to use for the ???
parts.

>
> import argparse
>
>
> parser = argparse.ArgumentParser(description="Shift bytes in a file")
>
> parser.add_argument("file", help="input file")
>
> parser.add_argument("-o", "--output", help="output file")
>
> parser.add_argument("-i", "--interval", help="byte interval",
> default=1000)
>
> parser.add_argument("-s", "--shift", help="size of shift", default=4)
>
> parser.add_argument("-k", "--skip", help="size of initial skip
> offset", default=128)
>
> args = parser.parse_args()
>
>
> filein = args.file
>
> fileout = args.output
>
> interval = int(args.interval)
>
> shift = int(args.shift)
>
> skip = int(args.skip)
>
>
> f = open(filein, "rb")
>
> out = open(fileout, "w+b")
>
>
> out.write( f.read1(skip) )
>
>
> while True:
>
> byte = f.read1(1)
>
> if byte == b'':
>
> break
>
>

I suspect the three lines above should be indented under the whilew like
this:

while True:
    byte = f.read1(1)
    if byte == "b":
         break


But I don't know if any of the lines below should be indented too...
The next 3 could be. And maybe they are in the original and its
the mail system thats destroyed them?

You need to post in plain text for us to accurately see the
original indentation levels (which are critically important in Python)


> lbfr = f.read(shift)
>
> rbfr = f.read(interval-shift)
>
> out.write(lbfr + byte + rbfr)
>
>
> f.close()
>
> out.close()
>
>
> This is what the cmd prompt says when I type in the new command
>
> C:\Users\natha> python D:\Python\bytsh.py D:\Video\test.mp4
> Traceback (most recent call last):
>   File "D:\Python\bytsh.py", line 18, in <module>
>     out = open(fileout, "w+b")
> TypeError: expected str, bytes or os.PathLike object, not NoneType
>
HTH

-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
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