Using session fixture as suggested by hpk42 is great solution for many cases,
but fixture will run only after all tests are collected.
Here are two more solutions:
conftest hooks
Write a pytest_configure or pytest_sessionstart hook in your conftest.py file:
# content of conftest.py
def pytest_configure(config):
"""
Allows plugins and conftest files to perform initial configuration.
This hook is called for every plugin and initial conftest
file after command line options have been parsed.
"""
def pytest_sessionstart(session):
"""
Called after the Session object has been created and
before performing collection and entering the run test loop.
"""
def pytest_sessionfinish(session, exitstatus):
"""
Called after whole test run finished, right before
returning the exit status to the system.
"""
def pytest_unconfigure(config):
"""
called before test process is exited.
"""
pytest plugin
Create a pytest plugin with pytest_configure and pytest_unconfigure hooks.
Enable your plugin in conftest.py:
# content of conftest.py
pytest_plugins = [
'plugins.example_plugin',
]
# content of plugins/example_plugin.py
def pytest_configure(config):
pass
def pytest_unconfigure(config):
pass