Python-How to take a dictionary as input

Question

Specs: Python3.3.2

What I intend to do:

Take a dictionary as input and return one as output, but the values are now the keys and vice versa

Question: I believe that I can figure out the key-and-value-switch part. But I don't know how to take a dictionary as input.(and keep the object type as dict)

What I tried:

a = input("Please enter a dictionary: ")
print(a)

Result: {'a':1,'b':2}. BUT:

This turned out to be a string object, as is shown using type(a) and getting <class 'str'> as result.

You could try the solution posted here: stackoverflow.com/questions/988228/… — pkacprzak
– pkacprzak, Commented Jun 23, 2013 at 19:02
Your "What I tried" part gives me a dict in the python 2.7 interpreter! — Atmaram Shetye
– Atmaram Shetye, Commented Jun 23, 2013 at 19:02
@zaphod: You're using Python 2, the OP is using Python 3. Try raw_input as an equivalent. — Markus Unterwaditzer
– Markus Unterwaditzer, Commented Jun 23, 2013 at 19:03
... well ... I'm not certain the OP as clearly understood the terms of his assignment? "Take a dictionary as input and return one as output" -- Should "input" be interpreted literally as "from the input() function"? Or, as I am inclined to think, should we understand "write a function receiving a dictionary as argument and returning an other one such as ..." Or am I just too tired to read things correctly? — Sylvain Leroux
– Sylvain Leroux, Commented Jun 23, 2013 at 19:07

enpenax · Accepted Answer · 2013-06-23 19:09:43Z

3

Everything you input in a terminal, will always be a string! Hence, if you enter a correct dict you have to transform it first by executing the given string like this:

import ast
a = input("Please enter a dictionary: ")
d = ast.literal_eval(a)
print d

However, looking at the comments to your question. I don't think somebody would ask you to parse a dict like that from the commandline. Hence, the task probably wants you to just write up a function to receive a dict and print it out, or probably play with it so you can see the difference between mutables and immutables in python and how they are passed around!

Cheers!

edited Jun 23, 2013 at 19:09

answered Jun 23, 2013 at 19:03

enpenax

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3 Comments

enpenax Over a year ago

@user2246674 It is seen around here very often. It's way better and safer than using eval().

Markus Unterwaditzer Over a year ago

Another option would be to use json.loads.

hakuna121 Over a year ago

Thanks! I think your reading of the question make more sense than mine. Parsing is a little too complicated for a beginner as I am right now.

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