Limit for stdout Lines Count in pytest

[horw]

Hello, my stdout is excessively long. Is there a way to limit the output, like showing only the last 100 lines?

[agammann]

If you want to keep the last 100 lines of captured stdout in each test report, a small conftest.py hook can trim just that section:

import pytest

@pytest.hookimpl(hookwrapper=True)
def pytest_runtest_makereport(item, call):
    outcome = yield
    report = outcome.get_result()
    report.sections[:] = [
        (heading, "\n".join(text.splitlines()[-100:]) + "\n")
        if heading.startswith("Captured stdout") else (heading, text)
        for heading, text in report.sections
    ]

I tested a failing test that prints 150 numbered lines on pytest 7.3.1 and 9.1.1; both reported exactly lines 050 through 149. This changes what pytest displays for a failed test, not how much output the application generates or pytest captures in memory. For simply hiding captured stdout altogether, --show-capture=no is simpler. TestReport.sections is documented.