Use pdb.set_trace() in a script that reads stdin via a pipe

Question

I have a python script that reads stdin via a pipe, and I cannot seem to use it with pdb.set_trace().

my_script.py:

#!/usr/bin/env python
import sy         


        

Answer 1

For completeness, I made a snippet with the following code, based on the accepted answer.

import sys; sys.stdin = open('/dev/tty'); import pdb; pdb.set_trace();

Answer 2

The thing is: cat will not stop sending data because your script is currently debugging. And when you going to trace, then stdin is still filled by cat + your keyboard. You need to choose one of them.

You can read the whole stdin, and then, set_trace() will be not filled by stdin:

sys.stdin.read()
pdb.set_trace()

Answer 3

Here's an example of what worked for me:

import sys
import pdb

lines = sys.stdin.readlines()
sys.stdin = open("/dev/tty")
pdb.set_trace()

Edit: since 3.7 you no longer need to import pdb for set_trace, it is available as breakpoint, so the above only requires a sys import.

import sys

lines = sys.stdin.readlines()
sys.stdin = open("/dev/tty")
breakpoint()

You may wish to replace sys.stdin.readlines() above with the iterable fileinput.input() (which defaults to sys.stdin if the list of files in sys.argv[1:] is empty) like so:

import fileinput
import sys

lines = fileinput.input()
sys.stdin = open("/dev/tty")
breakpoint()

Answer 4

Using the ripdb module (pip install ripdb) solved this issue for me.

Answer 5

You may want to look at how the Celery RDB (Remote Debugger) contrib module works:

https://github.com/celery/celery/blob/master/celery/contrib/rdb.py

It seems to involve a lot of stream processing, but I have tested it, and it works by allowing you to telnet into a new local network port. It's not the much better ipdb, but simply pdb.

Answer 6

I ran into this exact problem today. I found that Winpdb works perfectly.