get key from value python

Question

I have a txt file with a lot of lines like this

369136986 cms_trk_dcs_05:CAEN/CMS_TRACKER_SY1527_8/branchController05/easyCrate1/easyBoard03/channel002

Two columns where the first has numbers, and the second column a line with properties separated by /, both columns are separated by space.

I did a dictionary of dictionaries where the key1 is
the first number that appears in the line (369136986), this key has as a value the other dictionary, where the keys are cmstrk, trackersy, branch, crate, board, channel and each of these keys key has as a value cms_trk_dcs_05:CAEN, CMS_TRACKER_SY1527_8, branchController05, easyCrate1, easyBoard03, channel002, respectively, so if you ask cmstrk (key2) for 369136986 (key1) it returns cms_trk_dcs_05 (value).

How can I get the key by giving the value? I mean if I give the value CMS_TRACKER_SY1527_8 I need to know to which key1 corresponds (the program should return 369136986).

This is what i tried:

input3=raw_input("Write the property(s) which modules connected you want to know, separated by a single space \n > ")
input_list3=input3.split(' ')
for k in input_list3:
    print "%r" % k
    txt.write("\t\n The modules with property %r are:\n" % k)
    for l,m in zip(HVInfoDict.keys(),HVInfoDict.values()):
        if k == HVInfoDict[l][m]:
            print l

but it returns

TypeError: unhashable type: 'dict'

so how can I get the first key?

Does changing the if statement to if k in m.values(): get you what you want? — David Robinson
– David Robinson, Commented Jul 22, 2014 at 15:42
Could you put an example of the input dictionary that's a little easier to cut-and-paste? The problem here is that m is sometimes a dictionary, which can't be used as a key to another dictionary. — jonrsharpe
– jonrsharpe, Commented Jul 22, 2014 at 15:43
Also you can replace zip(HVInfoDict.keys(),HVInfoDict.values()) by HVInfoDict.items(), as it will return same list of tuples. — pavel_form
– pavel_form, Commented Jul 22, 2014 at 16:18
jonrsharpe, now it is solved thanks to David Robinson and Jhon Rudell, thanks for your comment. pavel_form thanks to you too — celonilanaparticle
– celonilanaparticle, Commented Jul 23, 2014 at 9:50

John Ruddell · Accepted Answer · 2014-07-22 16:18:36Z

1

m is the whole dictionary thats retured in HVInfoDict[l].. you need to look at the values inside of m like so.

HVInfoDict = {
    369136986: {
        'cmstrk': 'cms_trk_dcs_05:CAEN',
        'trackersy': 'CMS_TRACKER_SY1527_8',
        'branch': 'branchController05',
        'crate': 'easyCrate1',
        'board': 'easyBoard03',
        'channel': 'channel002'
    }
}

input3 = raw_input("Write the property(s) which modules connected you want to know, separated by a single space \n > ")
input_list3 = input3.split(' ')
for k in input_list3:
    print "%r" % k
    txt.write("\t\n The modules with property %r are:\n" % k)
    for l,m in HVInfoDict.items():
        if k in m.values():
            print l
        else:
            print("Does not exist!")

output:

Write the property(s) which modules connected you want to know, separated by a single space 
 > branchController05 CMS_TRACKER_SY1527_8 channel002 abcdefg
'branchController05'
369136986
'CMS_TRACKER_SY1527_8'
369136986
'channel002'
369136986
'abcdefg'
Does not exist!

edited Jul 22, 2014 at 16:18

answered Jul 22, 2014 at 16:03

John Ruddell

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1 Comment

celonilanaparticle Over a year ago

Jhon Rudell you are correct i was looking in the wrong place, thanks a lot for your ansewer, my script now works!

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