How can I Iterate over dictionaries using 'for' loops

0 votes

A bit puzzled by the following code:

d = {'x': 1, 'y': 2, 'z': 3} 
for key in d:
    print key, 'corresponds to', d[key]

What I don't understand is the key portion. How does Python recognize that it needs only to read the key from the dictionary? Is key a special word in Python? Or is it simply a variable?

Oct 17, 2018 in Python by findingbugs
• 4,750 points
77 views

1 answer to this question.

0 votes

key is just a variable name.

for key in d:

will simply loop over the keys in the dictionary, rather than the keys and values. To loop over both key and value you can use the following:

For Python 2.x:

for key, value in d.iteritems():

For Python 3.x:

for key, value in d.items():

To test for yourself, change the word key to poop.

For Python 3.x, iteritems() has been replaced with simply items(), which returns a set-like view backed by the dict, like iteritems() but even better. This is also available in 2.7 as viewitems().

The operation items() will work for both 2 and 3, but in 2 it will return a list of the dictionary's (key, value) pairs, which will not reflect changes to the dict that happen after the items() call. If you want the 2.x behavior in 3.x, you can call list(d.items()).

answered Oct 17, 2018 by Priyaj
• 56,900 points

Related Questions In Python

0 votes
1 answer

Iterating over dictionaries using 'for' loops

key is just a variable name. for key ...READ MORE

answered Oct 8, 2018 in Python by SDeb
• 13,160 points
51 views
+2 votes
2 answers

How can I replace values with 'none' in a dataframe using pandas

Actually in later versions of pandas this ...READ MORE

answered Aug 13, 2018 in Python by bug_seeker
• 15,350 points
6,699 views
+2 votes
2 answers

How can I plot a k-dsitance graph using python?

Hi there, instead of sklearn you could ...READ MORE

answered Apr 10, 2018 in Python by charlie_brown
• 7,720 points
1,257 views
+2 votes
2 answers

In a list of dictionaries, how can I find the minimum calue in a common dictionary field.

There are several options. Here is a ...READ MORE

answered Apr 10, 2018 in Python by charlie_brown
• 7,720 points
69 views
+1 vote
2 answers

how can i count the items in a list?

Syntax :            list. count(value) Code: colors = ['red', 'green', ...READ MORE

answered Jul 6 in Python by Neha
• 330 points

edited Jul 8 by Kalgi 282 views
+2 votes
3 answers

How can I play an audio file in the background using Python?

down voteacceptedFor windows: you could use  winsound.SND_ASYNC to play them ...READ MORE

answered Apr 3, 2018 in Python by charlie_brown
• 7,720 points
1,922 views
+1 vote
1 answer

How can I map input to output without using dynamic()

Here am talking about my example you ...READ MORE

answered Aug 8, 2018 in Python by Priyaj
• 56,900 points
144 views