Catch the stdout

The following example catches the python stdout and stderr:

basic.py

from contextlib import redirect_stdout, redirect_stderr
import syncstream

# Initialize the buffer.
buffer = syncstream.LineBuffer(10)

# Use contextlib to redirect stdout and stderr.
with redirect_stdout(buffer), redirect_stderr(buffer):
    for i in range(20):
        print('Message', f'"{i:02d}".')
    print('Line break\nin middle.', end='')
    print('No line break.', end='')

# Check the results
messages = buffer.read()
for mitem in messages:
    print(mitem)

In the definition of the buffer, we set the maximal number of catched lines as 10:

buffer = syncstream.LineBuffer(10)

The buffer instance could be passed to the redirect context. Inside the context, the print function would be redirected to the buffer. Each time a new line is detected, a new record item would be created by the buffer. The rules for detecting the new lines are the same as those of str.splitlines in the stdlib.

After catching all lines, the results could be returned by

messages = buffer.read()

Each item of messages is a str representing a line catched inside the context.