How do it I set the number of items in a key:value dictionary as the keys value in python

Question

Hello everyone I have an unique question.

In a key:value dictionary, how do I get the len of an item list and let the len be the keys value?

Such as

D = {'Chicago Cubs': 1907, 1908, 'World Series Not Played in 1904': [1904], 
     'Boston Americans': 1903, 'Arizona Diamondbacks': 2001, 
     'Baltimore Orioles':1966, 1970, 1983}


Chicago Cubs: 1907,1908

team = key and number of times shown = value

After counting the number of times the item appears in

Chicago Cubs - 2

What I need is:

Chicago Cubs: 2

What I have is:

D = {}
for e in l:
    if e[0] not in D:
        D[e[0]] = [e[1]]
    else:
      D[e[0]].append(e[1])

for k, v in sorted(D.items(), key=lambda x: -len(x[1])):
    max_team = ("%s - %s" % (k,len(v)))
    print(max_team)
return max_team

How should I go about this?

score 3 · Accepted Answer · answered Apr 01 '13 at 21:56

3

Your dictionary's syntax seems invalid try something like this (notice that all values have been enclosed in an array syntax):

D = {'Chicago Cubs': [1907, 1908], 'World Series Not Played in 1904': [1904],  'Boston Americans': [1903], 'Arizona Diamondbacks': [2001],  'Baltimore Orioles':[1966, 1970, 1983]}

And then use something like this (as it is more efficient since it only access items in the dictionary once.

newDict = {}
for key, value in D.iteritems():
     newDict [key] = len(value)

answered Apr 01 '13 at 21:56

Juan Carlos Moreno

2,754
3
22
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1

The second part can be done with a dict comprehension too: `N = { key:len(value) for key,value in D.iteritems() }` – askewchan Apr 01 '13 at 22:06
I am getting an error when I use `iteritems()` what should I do? I'm using python 3.3.0. – Thomas Jones Apr 01 '13 at 22:09
@askewchan: dict comp is only available in python 2.7+ – jdi Apr 01 '13 at 22:16
1

@ThomasJones: In py3 they were made generators by default [http://wiki.python.org/moin/Python3.0] - "Remove dict.iteritems(), dict.iterkeys(), and dict.itervalues(). Instead: use dict.items(), dict.keys(), and dict.values() respectively." – jdi Apr 01 '13 at 22:19

score 1 · Answer 2 · answered Apr 01 '13 at 21:52

1

I'm not sure I understood your question but give this a try:

d = {}
"""add some items to d"""

for key in d.keys():
    d[key] = len(d[key])

print d

answered Apr 01 '13 at 21:52

Ionut Hulub

6,180
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How do it I set the number of items in a key:value dictionary as the keys value in python

2 Answers2