Python iterate over a dictionary

Question

In [26]: test = {}

In [27]: test["apple"] = "green"

In [28]: test["banana"] = "yellow"

In [29]: test["orange"] = "orange"

In [32]: for fruit, colour in test:
   ....:     print fruit
   ....:     
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
/home1/users/joe.borg/<ipython-input-32-8930fa4ae2ac> in <module>()
----> 1 for fruit, colour in test:
      2     print fruit
      3 

ValueError: too many values to unpack

What I want is to iterate over test and get the key and value together. If I just do a for item in test: I get the key only.

An example of the end goal would be:

for fruit, colour in test:
    print "The fruit %s is the colour %s" % (fruit, colour)

Answer 1

In Python 2 you'd do:

for fruit, color in test.iteritems():
    # do stuff

In Python 3, use items() instead (iteritems() has been removed):

for fruit, color in test.items():
    # do stuff

This is covered in the tutorial.

Answer 2

Change

for fruit, colour in test:
    print "The fruit %s is the colour %s" % (fruit, colour)

to

for fruit, colour in test.items():
    print "The fruit %s is the colour %s" % (fruit, colour)

or

for fruit, colour in test.iteritems():
    print "The fruit %s is the colour %s" % (fruit, colour)

Normally, if you iterate over a dictionary it will only return a key, so that was the reason it error-ed out saying "Too many values to unpack". Instead items or iteritems would return a list of tuples of key value pair or an iterator to iterate over the key and values.

Alternatively you can always access the value via key as in the following example

for fruit in test:
    print "The fruit %s is the colour %s" % (fruit, test[fruit])

Answer 3

The normal for key in mydict iterates over keys. You want to iterate items:

for fruit, colour in test.iteritems():
    print "The fruit %s is the colour %s" % (fruit, colour)