How to debug python CLI that takes stdin?

Another option is to create you own Pdb object, and set there the stdin and stdout. My proof of concept involves 2 terminals, but for sure some work can be merged some kind of very unsecure network server.

1. Create two fifos:

   mkfifo fifo_stdinmkfifo fifo_stdout

2. In one terminal, open stdout on background, and write to stdin:

   cat fifo_stdout &cat > fifo_stdin

3. In your python code/console create the pdb object, and use it:

   import pdbmypdb=pdb.Pdb(stdin=open('fifo_stdin','r'), stdout=open('fifo_stdout','w'))...mypdb.set_trace()...

4. Profit!

You should be able to use pdb on the first console.

The only drawback is having to use your custom pdb, but some monkey patching at init (PYTHONSTARTUP or similar) can help:

import pdbmypdb=pdb.Pdb(stdin=open('fifo_stdin','r'), stdout=open('fifo_stdout','w'))pdb.set_trace=mypdb.set_trace

You can use another file descriptor. With bash you can create a new file descriptor with:

exec 3<> test.txt

And then on your python file have something like:

#!/usr/bin/python# Use fd 3 as another stdin file.import osstdin=os.fdopen(3)while True:    s=stdin.readline()    import pdb; pdb.set_trace()    print len(s)

Just runing your script will use that test.txt as input, and you can use stdin on stdin. It can be used as well with pipes if you need.

Your controlling TTY is still a terminal, right? Use this instead of pdb.set_trace.

def tty_pdb():    from contextlib import (_RedirectStream,                            redirect_stdout, redirect_stderr)    class redirect_stdin(_RedirectStream):        _stream = 'stdin'    with open('/dev/tty', 'r') as new_stdin, \         open('/dev/tty', 'w') as new_stdout, \         open('/dev/tty', 'w') as new_stderr, \         redirect_stdin(new_stdin), \         redirect_stdout(new_stdout), redirect_stderr(new_stderr):        __import__('pdb').set_trace()

Haven't gotten readline to autocomplete under these circumstances. Up arrow won't work either, or any other of the readline niceties.