python3 dictionary, values as a list

Question

The following code does not have any problem in Python 2.7, however in Python 3.4.3, throws TypeError: iteration over a 0-d array

import numpy as np
def c1():
        mat=[]
        mat.append(np.array(map(float,np.random.rand(7))))
        return mat
mylist=[]
mydict_={}
mydict_['dog']=c1()
mydict_['big']=c1()

justKeys={label:1 for label in list(mydict_.keys())}

for idx, word in enumerate(justKeys.keys()):
        mylist.append(np.array(map(float, mydict_[word][0])))

What should I do in order to the list mylist in both python2.7 and 3.4 get the same results?

Answer 1

The issue is not with the dictionary methods, but the map function, which is changed in Python 3 to return an iterator rather than a list. Numpy doesn't handle the iterators properly, so you need to add a list call to fix things:

def c1():
    mat=[]
    mat.append(np.array(list(map(float,np.random.rand(4,7)))))
    return mat

The rest of your code is a bit confusing, as you're creating a new dictionary, without any useful contents, then enumerating the keys of the new dictionary without using the indexes. It seems like you could just use my_list = [x[0] for x in dict_.values()] and have the same result (since the first item in the value lists is already a numpy array of floats, once you fix c1 as above).