Re: Python multimap
Carl Banks wrote: Out of curiosity, what does a true multimap solve that a dictionary of lists not solve? Nothing really. I went with a variation of the suggested work around... it's just that with Python I don't normally have to use work arounds and normally one obvious approach is correct: -- http://mail.python.org/mailman/listinfo/python-list
Re: Python multimap
On Aug 28, 2:41 pm, brad [EMAIL PROTECTED] wrote: Carl Banks wrote: Out of curiosity, what does a true multimap solve that a dictionary of lists not solve? Nothing really. I went with a variation of the suggested work around... it's just that with Python I don't normally have to use work arounds and normally one obvious approach is correct: Might I suggest that the C++ multimap is the workaround, rather than the Python way of using dicts or lists or dicts of sets? It was too much programming overhead and line noise confusion to define nested templates to hold your nested data structures in C++, so the STL provided a container that eliminated the nesting. In Python, the obvious nested way to do it is easy, especially now with defaultdicts, so there was no reason to provide a multimap. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
Python multimap
Recently had a need to us a multimap container in C++. I now need to write equivalent Python code. How does Python handle this? k['1'] = 'Tom' k['1'] = 'Bob' k['1'] = 'Joe' ... Same key, but different values. No overwrites either They all must be inserted into the container Thanks, Brad -- http://mail.python.org/mailman/listinfo/python-list
Re: Python multimap
On Aug 27, 9:35 am, brad [EMAIL PROTECTED] wrote:
Recently had a need to us a multimap container in C++. I now need to
write equivalent Python code. How does Python handle this?
k['1'] = 'Tom'
k['1'] = 'Bob'
k['1'] = 'Joe'
...
Same key, but different values. No overwrites either They all must
be inserted into the container
Thanks,
Brad
Python 2.5.2 (r252:60911, Jul 31 2008, 17:28:52)
[GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2
Type help, copyright, credits or license for more information.
k = {}
k['1'] = []
k['1'].append('Tom')
k['1'].append('Bob')
k['1'].append('Joe')
k['1']
['Tom', 'Bob', 'Joe']
--
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Re: Python multimap
brad wrote:
Recently had a need to us a multimap container in C++. I now need to
write equivalent Python code. How does Python handle this?
k['1'] = 'Tom'
k['1'] = 'Bob'
k['1'] = 'Joe'
...
Same key, but different values. No overwrites either They all must
be inserted into the container
Thanks,
Brad
I don't know if this is exactly equivalent, but what about using a
defaultdict like this?
from collections import defaultdict
k = defaultdict(list)
k['1'].append('Tom')
k['1'].append('Bob')
k['1'].append('Joe')
k['1']
['Tom', 'Bob', 'Joe']
--
--
http://mail.python.org/mailman/listinfo/python-list
Re: Python multimap
brad wrote: Recently had a need to us a multimap container in C++. I now need to write equivalent Python code. How does Python handle this? k['1'] = 'Tom' k['1'] = 'Bob' k['1'] = 'Joe' Same key, but different values. No overwrites either They all must be inserted into the container Subclassing the builtin dict? class d(dict): def __setitem__(self, item, value): if not item in self: super(d, self).__setitem__(item, []) self[item].append(value) D = d() D[1] = Hello D[1] = World! D[1] ['Hello', 'World!'] Thanks, Brad Michele -- http://mail.python.org/mailman/listinfo/python-list
Re: Python multimap
Mike Kent wrote:
Python 2.5.2 (r252:60911, Jul 31 2008, 17:28:52)
[GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2
Type help, copyright, credits or license for more information.
k = {}
k['1'] = []
k['1'].append('Tom')
k['1'].append('Bob')
k['1'].append('Joe')
k['1']
['Tom', 'Bob', 'Joe']
There is only one '1' key in your example. I need multiple keys that are
all '1'. I thought Python would have something built-in to handle this
sort of thing.
I need a true multimap:
k['1'] = 'Tom'
k['1'] = 'Tommy'
without Tommy overwriting Tom and without making K's value a list of
stuff to append to. That's still just a regular map.
--
http://mail.python.org/mailman/listinfo/python-list
Re: Python multimap
brad wrote: There is only one '1' key in your example. I need multiple keys that are all '1'. I thought Python would have something built-in to handle this sort of thing. I need a true multimap ... without making K's value a list of stuff to append to. That's what a multimap is. If you really need the syntactic sugar, it's simple to implement: class multidict(dict): def __setitem__(self, key, value): try: self[key].append(value) except KeyError: dict.__setitem__(self, key, [value]) -Miles -- http://mail.python.org/mailman/listinfo/python-list
Re: Python multimap
On Aug 27, 12:52 pm, brad [EMAIL PROTECTED] wrote:
Mike Kent wrote:
Python 2.5.2 (r252:60911, Jul 31 2008, 17:28:52)
[GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2
Type help, copyright, credits or license for more information.
k = {}
k['1'] = []
k['1'].append('Tom')
k['1'].append('Bob')
k['1'].append('Joe')
k['1']
['Tom', 'Bob', 'Joe']
There is only one '1' key in your example. I need multiple keys that are
all '1'. I thought Python would have something built-in to handle this
sort of thing.
I need a true multimap:
k['1'] = 'Tom'
k['1'] = 'Tommy'
without Tommy overwriting Tom and without making K's value a list of
stuff to append to. That's still just a regular map.
I don't understand what a multimap does that a map of lists doesn't do.
--
http://mail.python.org/mailman/listinfo/python-list
Re: Python multimap
castironpi wrote: I don't understand what a multimap does that a map of lists doesn't do. It counts both keys individually as separate keys. The Python workaround does not... see examples... notice the key(s) that are '4' Python output (using the k = [] idea): Key: 4 Value: [[13, 'Visa'], [16, 'Visa']] Key: 51 Value: [16, 'MC'] Key: 65 Value: [16, 'Discover'] Key: 2131 Value: [15, 'JCB'] Key: 300 Value: [14, 'Diners CB'] Key: 301 Value: [14, 'Diners CB'] Key: 302 Value: [14, 'Diners CB'] Key: 303 Value: [14, 'Diners CB'] Key: 304 Value: [14, 'Diners CB'] Key: 305 Value: [14, 'Diners CB'] Key: 35 Value: [16, 'JCB'] Key: 34 Value: [15, 'Amex'] Key: 55 Value: [16, 'MC or Diners US and CA'] Key: 36 Value: [14, 'Diners Intl'] Key: 37 Value: [15, 'Amex'] Key: 1800 Value: [15, 'JCB'] Key: 54 Value: [16, 'MC'] Key: 6011 Value: [16, 'Discover'] Key: 52 Value: [16, 'MC'] Key: 53 Value: [16, 'MC'] Key: 385 Value: [14, 'Diners CB'] 21 is the size of the dict A C++ multimap Key: 1800 Value: JCB 15 Key: 2131 Value: JCB 15 Key: 300 Value: Diners_Club 14 Key: 301 Value: Diners_Club 14 Key: 302 Value: Diners_Club 14 Key: 303 Value: Diners_Club 14 Key: 304 Value: Diners_Club 14 Key: 305 Value: Diners_Club 14 Key: 34 Value: American_Express 15 Key: 35 Value: JCB 16 Key: 36 Value: Diners_Club 14 Key: 37 Value: American_Express 15 Key: 385 Value: Diners_Club 14 Key: 4 Value: Visa 16 Key: 4 Value: Visa 13 Key: 51 Value: MasterCard 16 Key: 52 Value: MasterCard 16 Key: 53 Value: MasterCard 16 Key: 54 Value: MasterCard 16 Key: 55 Value: MasterCard 16 Key: 6011 Value: Discover 16 Key: 65 Value: Discover 16 22 is the size of the multimap -- http://mail.python.org/mailman/listinfo/python-list
Re: Python multimap
Miles wrote: That's what a multimap is. iirc, a C++ multimap provides a flat view of the data, so you need to provide custom enumeration and iteration methods as well. /F -- http://mail.python.org/mailman/listinfo/python-list
Re: Python multimap
On Aug 27, 1:38 pm, brad [EMAIL PROTECTED] wrote: castironpi wrote: I don't understand what a multimap does that a map of lists doesn't do. It counts both keys individually as separate keys. The Python workaround does not... see examples... notice the key(s) that are '4' Python output (using the k = [] idea): Key: 4 Value: [[13, 'Visa'], [16, 'Visa']] A C++ multimap Key: 4 Value: Visa 16 Key: 4 Value: Visa 13 You are looking at a two-line workaround. A single Key-4 element is always k[4][0], if 4 is in k. To remove k[4] is a little trickier. If len( k[4] ) 1: k[4].pop( ), else k.pop( 4 )[ 0 ]. (Smooth.) -- http://mail.python.org/mailman/listinfo/python-list
Re: Python multimap
On Aug 27, 1:52 pm, brad [EMAIL PROTECTED] wrote:
Mike Kent wrote:
Python 2.5.2 (r252:60911, Jul 31 2008, 17:28:52)
[GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2
Type help, copyright, credits or license for more information.
k = {}
k['1'] = []
k['1'].append('Tom')
k['1'].append('Bob')
k['1'].append('Joe')
k['1']
['Tom', 'Bob', 'Joe']
There is only one '1' key in your example. I need multiple keys that are
all '1'. I thought Python would have something built-in to handle this
sort of thing.
I need a true multimap:
k['1'] = 'Tom'
k['1'] = 'Tommy'
without Tommy overwriting Tom and without making K's value a list of
stuff to append to. That's still just a regular map.
What would you want to happen if you were to execute print k['1']?
Best I can tell, you want some sort of association list like this:
k = []
k.append((1,Tom))
k.append((1,Tommy))
which you can iterate through like this:
for key,value in k:
And if you need to retrieve items with a certain key, probably it's
easiest to maintain sorted invariant, and to do insertion and lookup
with bisection algorithm (see bisect module).
I don't know of any class in the standard library that does all that
for you though.
Out of curiosity, what does a true multimap solve that a dictionary of
lists not solve?
Carl Banks
--
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