Python: Using a dictionary to count the items in a list

Question

I'm new to Python and I have a simple question, say I have a list of items:

['apple','red','apple','red','red','pear']

Whats the simpliest way to add the list items to a dictionary and count how many times the item appears in the list.

So for the list above I would like the output to be:

{'apple': 2, 'red': 3, 'pear': 1}

Answer 1

>>> L = ['apple','red','apple','red','red','pear']
>>> from collections import defaultdict
>>> d = defaultdict(int)
>>> for i in L:
...   d[i] += 1
>>> d
defaultdict(<type 'int'>, {'pear': 1, 'apple': 2, 'red': 3})

Answer 2

One Liner:

l = ['apple','red','apple','red','red','pear']

print dict((item, l.count(item)) for item in set(l))

{'pear': 1, 'apple': 2, 'red': 3}

Answer 3

L = ['apple','red','apple','red','red','pear']
d = {}
[d.__setitem__(item,1+d.get(item,0)) for item in L]
print d 

Gives {'pear': 1, 'apple': 2, 'red': 3}

Answer 4

in 2.7 and 3.1 there is special Counter dict for this purpose.

>>> from collections import Counter
>>> Counter(['apple','red','apple','red','red','pear'])
Counter({'red': 3, 'apple': 2, 'pear': 1})

Answer 5

I always thought that for a task that trivial, I wouldn't want to import anything. But i may be wrong, depending on collections.Counter being faster or not.

items = "Whats the simpliest way to add the list items to a dictionary "

stats = {}
for i in items:
    if i in stats:
        stats[i] += 1
    else:
        stats[i] = 1

# bonus
for i in sorted(stats, key=stats.get):
    print("%d×'%s'" % (stats[i], i))

I think this may be preferable to using count(), because it will only go over the iterable once, whereas count may search the entire thing on every iteration. I used this method to parse many megabytes of statistical data and it always was reasonably fast.