Standard input is empty

a
 11           0 LOAD_GLOBAL              0 (getattr)
              3 LOAD_GLOBAL              1 (obj)
              6 LOAD_CONST               1 ('frob')
              9 CALL_FUNCTION            2 (2 positional, 0 keyword pair)
             12 POP_TOP
             13 LOAD_CONST               0 (None)
             16 RETURN_VALUE
========================================
b
 14           0 LOAD_GLOBAL              0 (obj)
              3 LOAD_ATTR                1 (frob)
              6 POP_TOP
              7 LOAD_CONST               0 (None)
             10 RETURN_VALUE
========================================
c
 17           0 LOAD_GLOBAL              0 (obj)
              3 LOAD_ATTR                1 (frob)
              6 CALL_FUNCTION            0 (0 positional, 0 keyword pair)
              9 POP_TOP
             10 LOAD_CONST               0 (None)
             13 RETURN_VALUE
========================================
d
 20           0 LOAD_GLOBAL              0 (obj)
              3 LOAD_ATTR                1 (frob)
              6 STORE_FAST               0 (frob)

 21           9 LOAD_FAST                0 (frob)
             12 CALL_FUNCTION            0 (0 positional, 0 keyword pair)
             15 POP_TOP
             16 LOAD_CONST               0 (None)
             19 RETURN_VALUE
========================================