Iterating over key and value of defaultdict dictionaries

Question

The following works as expected:

d = [(1,2), (3,4)]
for k,v in d:
  print "%s - %s" % (str(k), str(v))

But this fails:

d = collections.defaultdict(int)
d[1] = 2
d[3] = 4
for k,v in d:
  print "%s - %s" % (str(k), str(v))

With:

Traceback (most recent call last):  
 File "<stdin>", line 1, in <module>  
TypeError: 'int' object is not iterable

Why? How can i fix it?

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Answer 1

you need to iterate over dict.iteritems():

for k,v in d.iteritems():               # will become d.items() in py3k
  print "%s - %s" % (str(k), str(v))

Update: in py3 V3.6+

for k,v in d.items():
  print (f"{k} - {v}")

Answered By: SilentGhost

Answer 2

if you are using Python 3.6

from collections import defaultdict

for k, v in d.items():
    print(f'{k} - {v}')

Answered By: Vlad Bezden

Answer 3

If you want to iterate over individual item on an individual collection:

from collections import defaultdict

for k, values in d.items():
    for value in values:
       print(f'{k} - {value}')

Answered By: Nguai al

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