Python stdout.readline() freeze

Question

i'm using in my python script:

cmd = ["checkcode.exe", "code=1234"]
proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, close)
result = proc.stdout.readline()

checkcode.exe return a value, or nothing, and stay alive

All works fine when checkcode.exe return a value, but when checkcode.exe don't return value, the script block at result = proc.stdout.readline()

How to resolve the problem?

Answer 1

You must ensure that the subprocess exits in order to prevent readline() from blocking. The readline waits until it receives a newline or end-of-file. EOF is achieved on program exit.

Alternatively, you can use non-blocking I/O as mentioned in the comment above.