Python dictionary get method in assignment

Question

All,

I'm looping over a dictionary and counting the values that occur. To do this, I'm using the get method in the assignment statement for another dictionary. This returns a syntax error "can't assign to function call"

counts = {}
mydict = {'a':[1,2,5], 'b': [1,2,10]}
for key,value in mydict.iteritems():
    counts(value[1]) = counts.get(value[1], 0) + 1

Why would the assignment try to point to the function, rather than the return value?

Answer 1

counts = {}
mydict = {'a':[1,2,5], 'b': [1,2,10]}
for key,value in mydict.iteritems():
    counts[value[1]] = counts.get(value[1], 0) + 1

You need brackets, not parenthesis, to get an item from a dictionary.

Also, You're doing this the hard way.

from collections import defaultdict

# automatically start each count at zero
counts = defaultdict(int)
# we only need the values, not the keys
for value in mydict.itervalues(): 
    # add one to the count for this item
    counts[value[1]] += 1

or

# only on Python 2.7 or newer
from collections import Counter

counts = Counter(value[1] for value in mydict.itervalues())

Answer 2

Instead of counts(value[1]) = ... you want counts[value[1]] = ....

Answer 3

Change this:

counts(value[1])

to this:

counts[value[1]]

Code looks like this:

counts = {}
mydict = {'a':[1,2,5], 'b': [1,2,10]}
for key, value in mydict.iteritems():
    counts[value[1]] = counts.get(value[1], 0) + 1

Answer 4

counts[value[1]] = counts.get(value[1], 0) + 1

should be

counts[value[1]] = counts.get(value[1], 0) + 1