Python - Dictionaries - Print a key given the value

Question

I'm new to programming, sorry if this is a silly question. From a dictionary (I'm aware there are other ways to do this), I want to be able to print out the value (or key, I get them confused) of a dictionary item. For example: d = {'print this':'given this'}

>>> d['given this']
Traceback (most recent call last):
  File "<pyshell#16>", line 1, in <module>
    d['given this']
KeyError: 'given this'
>>>

However, this works.

>>> d['print this']
'given this'
>>>

So I know there must be a way to get it to give me that variable. One thing I am confused on is this.

>>> for i in d:
    print(i + d[i])


print thisgiven this
>>>

How come I am able to print out both of the strings when I have a for loop?

Sorry if I did not post correctly, please tell me what I should change to make my question easier to answer.

Also please note, I have tried finding out the answer to this myself. I briefly learned about the "get" method, but I was having trouble getting it to do what I wanted to do. Thanks :)

http://stackoverflow.com/questions/8023306/get-key-by-value-in-dictionary — Two-Bit Alchemist, Mar 17 '14 at 21:00
You access dictionary items by their key, NEVER by their item. So you have to `print 'print this' + d['print this']` to produce `print this given this` — AndyG, Mar 17 '14 at 21:00
Alright, thank you for the answers. I was rather surprised there was no better solution to my problem, however. — Kyle Me, Mar 17 '14 at 21:05
That's just the nature of mappings. They're designed for lookup by key, not by value. — Kirk Strauser, Mar 17 '14 at 21:06

score 1 · Answer 1 · answered Mar 17 '14 at 21:08

1

print [(key, value) for key, value in d.items ()
           if value == value_you_search_for]

Keep in mind, that this can give you zero, one or more items - while keys are unique, values don't need to be.

answered Mar 17 '14 at 21:08

m.wasowski

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score 0 · Answer 2 · answered Mar 17 '14 at 21:07

0

You can't directly access a key by a given value. What you could do is this:

for key, value in d.iteritems() :
    print value,key

answered Mar 17 '14 at 21:07

Alex Koukoulas

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score 0 · Answer 3 · answered Mar 17 '14 at 21:08

0

Why don't you try:

for key, value in d.iteritems():
    print(key+value)

answered Mar 17 '14 at 21:08

praba230890

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Python - Dictionaries - Print a key given the value

3 Answers3