ternary if not none optional parameter isinstance list

# python if statements short circuit BUT be careful using not

a = list()
if not a:
  print 'empty list'

a = None
if not a:
  print 'None'

a = ''
if not a:
    print 'empty string'

# explicit checking can avoid nasty bugs later
if result is not None and len( result ) == 0:


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# ternary operator, very useful for optional parameters  def foo( num=None, mylist=None ):
num = num if num else 0     # assign num to 0 by default (if it's None or empty or ...)
mylist = mylist if mylist else []   # store the passed list or assign empty list


assert not isinstance( lst, basestring )        #   input is a list or tuple (not a string)