flask 源码专题（一）：请求上下文与全文上下文

if __name__ == ‘__main__‘:
    app.run()

def run(self, host=None, port=None, debug=None,
        load_dotenv=True, **options):
    # Change this into a no-op if the server is invoked from the
    # command line. Have a look at cli.py for more information.
    if os.environ.get(‘FLASK_RUN_FROM_CLI‘) == ‘true‘:
        from .debughelpers import explain_ignored_app_run
        explain_ignored_app_run()
        return
 
    if get_load_dotenv(load_dotenv):
        cli.load_dotenv()
 
        # if set, let env vars override previous values
        if ‘FLASK_ENV‘ in os.environ:
            self.env = get_env()
            self.debug = get_debug_flag()
        elif ‘FLASK_DEBUG‘ in os.environ:
            self.debug = get_debug_flag()
 
    # debug passed to method overrides all other sources
    if debug is not None:
        self.debug = bool(debug)
 
    _host = ‘127.0.0.1‘
    _port = 5000
    server_name = self.config.get(‘SERVER_NAME‘)
    sn_host, sn_port = None, None
 
    if server_name:
        sn_host, _, sn_port = server_name.partition(‘:‘)
 
    host = host or sn_host or _host
    port = int(port or sn_port or _port)
 
    options.setdefault(‘use_reloader‘, self.debug)
    options.setdefault(‘use_debugger‘, self.debug)
    options.setdefault(‘threaded‘, True)
 
    cli.show_server_banner(self.env, self.debug, self.name, False)
 
    from werkzeug.serving import run_simple
 
    try:
        run_simple(host, port, self, **options)
    finally:
        # reset the first request information if the development server
        # reset normally.  This makes it possible to restart the server
        # without reloader and that stuff from an interactive shell.
        self._got_first_request = False