try: import ast from pip._vendor._markerlib.markers import default_environment, compile, interpret except ImportError: if 'ast' in globals(): raise def default_environment(): return {} def compile(marker): def marker_fn(environment=None, override=None): # 'empty markers are True' heuristic won't install extra deps. return not marker.strip() marker_fn.__doc__ = marker return marker_fn def interpret(marker, environment=None, override=None): return compile(marker)()