On 4/10/2014 7:02 PM, length power wrote: > >>> "ok" or "not ok" > 'ok' > >>> "ok" and "not ok" > 'not ok' > >>> > > why "ok" or "not ok" output "ok" , "ok" and "not ok" output "not ok" ? This is explained in our fine manual. https://docs.python.org/2/reference/expressions.html#boolean-operations -- Terry Jan Reedy