python list conprehension error: global name is not defined

Question

I came across a weird issue. The error message is : global name 'id2tag' is not defined. I have read this post Accessing class variables from a list comprehension in the class definition. But obviously id2tag is not a class variable. The code is listed below.

class evaluater:
    def evaluate_topk(self, ground_truth_dict, predicted_dict, setting_name, setting, data,
                      eval_root_dir = './', file_name = 'result',k = 5,output_entry = 100 ):
        #this part of code is not relevant
        recall = {}
        for key, ground_truth in ground_truth_dict.items():
            recall[key] = recall_at_k(ground_truth, predicted_dict[key])

        mean_recall = np.mean([value for key,value in recall.items()])

        filepath = eval_root_dir + file_name
        if not os.path.exists(os.path.dirname(filepath)):
            os.makedirs(os.path.dirname(filepath))        

        #HERE IS WHERE id2tag DEFINED
        id2tag = {row[0]:row[1] for row in data[config.TYPE_TAG] }
        with open( filepath , 'a' ) as file:
            for itemid in sorted(ground_truth_dict.keys())[1:100]:
                file.write(str(itemid) + '\n')

                file.write('gnd:'+str([id2tag[id] for id in ground_truth_dict[itemid]] ) + '\n')
                file.write('prt' + str([ id2tag[id] for id in predicted_dict[itemid]]) + '\n' )
                #if i use the below code instead, then would be fine
                #gnd_tags = []
                #prt_tags = []
                #for id in ground_truth_dict[itemid]:
                #    gnd_tags.append(id2tag[id])
                #    
                #for id in predicted_dict[itemid]:
                #    prt_tags.append(id2tag[id])
                #    
                #file.write('gnd:'+str( gnd_tags ) + '\n')
                #file.write('prt' + str(prt_tags) + '\n' )

        return mean_recall

Something's wrong with the indentation in your post. Could you fix it? (It could actually be your problem if it turns out to be way off from how it's visible here.) — icktoofay, Mar 17 '14 at 01:46
`global name XXXX is not defined` almost always means you've made a typo in your code and are trying to reference a variable that hasn't been assigned yet. What line number does it say the error occurs on? — aruisdante, Mar 17 '14 at 01:52
Beyond the indentation, there's a lot of stuff going on in this code. It's nicer (and more likely to get people to help you) if you come up with a minimal example -- that is, cut out as much of the code as possible so that you just end up with the part relevant to the question. — Pandu, Mar 17 '14 at 02:36

score 1 · Answer 1 · answered Mar 17 '14 at 04:40

1

Syntax error in your complex embedded code. I think your weird issue will disappear, if you split your one line code to three:

# Change this line 
id2tag = {row[0]:row[1] for row in data[config.TYPE_TAG]}

# Change to this
id2tag = {}
for row in data[config.TYPE_TAG]:
    id2tag[row[0]] = row[1]

BTW: I'd suggest not use embedded for x in list_var in your way, which is not very easy to read and understand for other code readers.

answered Mar 17 '14 at 04:40

stanleyxu2005

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This is a legit dictionary comprehension as far as I can tell, where is the syntax error? – kynan Oct 20 '16 at 17:53

score 0 · Answer 2 · edited May 23 '17 at 12:03

This is a weird issue. I encountered it when debugging inside namespace of a class function in py.test in pdb. Outside of pdb there was no error.

(Pdb) lines=["oneline",2,3,4,5]
(Pdb) ip_dict = dict( ( lines[i], lines[i+1] ) for i in range(0,len(lines),2) )
*** NameError: global name 'lines' is not defined
(Pdb) for i in range(0,len(lines),2): print "%d=%s" % (i,lines[i])
0=oneline
2=3
4=5

(Pdb) self
<Docker-sanity_regression.SANITY testMethod=test_SANITY_002_####_container>

To simplify the problem here is an example.

lines=["oneline",2,3,4,5]
ip_dict = dict( ( lines[i], lines[i+1] ) for i in range(0,len(lines),2) )
print ip_dict

This works fine for python 2.4. And python 2.7. Embedding the dict set in a class func:

class Test:
    def __init__(self):
        print "init"
        self.ip_dict = {}

    def setDict(self):
        lines=["oneline",2,3,4,5]
        self.ip_dict = dict( ( lines[i], lines[i+1] ) for i in range(0,len(lines),2) )
        print self.ip_dict

foo = Test()
foo.setDict()

This also works fine for python 2.4. And python 2.7.

So I am thinking there is a funny namespace problem in certain versions of python and pdb for this type of comprehension. EDIT: Yes. Known issue for pdb. Thanks to https://stackoverflow.com/users/396967/kynan for explaining. https://bugs.python.org/issue21161 Title: list comprehensions don't see local variables in pdb in python3

[There is indeed](https://bugs.python.org/issue21161): pdb does not see local variables in list comprehensions, generator expressions and lambdas. [workaround](https://bugs.python.org/issue21161#msg215963): interact drops into an interactive shell where scoping works as expected — kynan, Oct 20 '16 at 17:55

python list conprehension error: global name is not defined

2 Answers2