try vs. has_key()

[Jeremy Hylton]

>>>>> "WD" == William H Duquette <William.H.Duquette at jpl.nasa.gov> writes:

  WD> As someone pointed out, append() returns None, explaining the
  WD> result I got.  However, the following code works just fine:
 d = {}
 a = 'foo'

 # Append an entry to d[a], whether it has been initialized or not:
 d[a] = d.get(a, [])
 d[a].append('Bar')

However, you're doing two dictionary lookups when only one is
necessary.  It would be more efficient to store the results of the get 
in a temporary variable -- temp = d[a] = d.get(a, []) -- and use the
temporary variable for the append.

Jeremy