[Tutor] Having list in dict type

[Danny Yoo]

On Tue, 4 Dec 2001, Mariappan, MaharajanX wrote:

> Hi Folks!
> 
> Is it posible for dictionary type's value part to be a list like below,
> 
> { "key1", ["name", "value"]
>   "key2", ["name", "value"]

Sure: if we try this in the interpreter:

###
>>> mydict = {}
>>> mydict = { "key" : ['name', 'value'],
...            'key2' : ['name', 'value'] }
>>> mydict
{'key': ['name', 'value'], 'key2': ['name', 'value']}
###

we can see that this works well.  Python's data structures can be nested
arbitrarily deep, so we can even do something very silly like this with
lists:

###
>>> def cover(thing, depth):
...     while depth > 0:
...         thing = [thing]
...         depth = depth - 1
...     return thing
... 
>>> buried_treasure = cover('gold coin', 10)
>>> buried_treasure
[[[[[[[[[['gold coin']]]]]]]]]]
###


and this flexibility extends to dictionaries too:

###
>>> treasures_of_the_deep = { 'gold coin' : cover('gold coin', 10),
...                           'mythril' : cover('mythril', 7),
...                           'masamune' : cover('masamune', 14) }
>>> treasures_of_the_deep
{ 'mythril': [[[[[[['mythril']]]]]]],
  'masamune': [[[[[[[[[[[[[['masamune']]]]]]]]]]]]]],
  'gold coin': [[[[[[[[[['gold coin']]]]]]]]]] }
###



> 1) how can I gennerate this data dynamically[ Asuume that I have all
> the sting values]

This depends on how your data is organized.  If it looks like you're
traversing, one by one, through your string values, then using a 'for'
loop might work well.  Can you give us some sample data, and your
expectation of what the dictionary should look like?


We can always add new entries into a dictionary like this:

###
>>> treasures_of_the_deep['pearl'] = cover('pearl', 99)
###

so if we combine something like this with a loop, we should be able to
insert elements dynamically into a dictionary.



> 2) Hiw can I traverse and print all the strings from this data.

We can 'walk' down dictionaries with the items() method.  For example,
with that dictionary above:

###
>>> mydict = { "key" : ['name', 'value'],
...            'key2' : ['name', 'value'] }
>>> for key, value in mydict.items():
...     print "The key %s unlocks the value %s" % (key, value)
... 
The key key unlocks the value ['name', 'value']
The key key2 unlocks the value ['name', 'value']
###

You might want to look at the dictionary documentation here:

    http://www.python.org/doc/lib/typesmapping.html

which covers what we can do with dictionaries in excruciating detail.  
It's not thrilling reading, but it might come in handy.


Hope this helps!