passing a variable to cmd

[Terry Reedy]

On 11/6/2016 6:48 AM, SS wrote:

> cmd="dig @4.2.2.2 %s ns +short", % (domname)
>
> does not work.

No kidding.  ', %' is a syntax error.  The , makes a tuple, the % after 
string does interpolation.  You obviously want the latter so omit the ,.

The traceback should have pointed you to where the code became invalid.

 >>> cmd="dig @4.2.2.2 %s ns +short", % (domname)
   File "<stdin>", line 1
     cmd="dig @4.2.2.2 %s ns +short", % (domname)
                                      ^
This mean that % is not valid GIVEN WHAT HAS COME BEFORE being treated 
as correct.  The , could have been correct, so Python cannot know it is 
incorrect here.

-- 
Terry Jan Reedy