How to print a dictionary's key?

Question

I would like to print a specific Python dictionary key:

mydic = {}
mydic[\'key_name\'] = \'value_name\'

Now I can check if mydic.has_

Answer 1

I'm adding this answer as one of the other answers here (https://stackoverflow.com/a/5905752/1904943) is dated (Python 2; iteritems), and the code presented -- if updated for Python 3 per the suggested workaround in a comment to that answer -- silently fails to return all relevant data.

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Background

I have some metabolic data, represented in a graph (nodes, edges, ...). In a dictionary representation of those data, keys are of the form (604, 1037, 0) (representing source and target nodes, and the edge type), with values of the form 5.3.1.9 (representing EC enzyme codes).

Find keys for given values

The following code correctly finds my keys, given values:

def k4v_edited(my_dict, value):
    values_list = []
    for k, v in my_dict.items():
        if v == value:
            values_list.append(k)
    return values_list

print(k4v_edited(edge_attributes, '5.3.1.9'))
## [(604, 1037, 0), (604, 3936, 0), (1037, 3936, 0)]

whereas this code returns only the first (of possibly several matching) keys:

def k4v(my_dict, value):
    for k, v in my_dict.items():
        if v == value:
            return k

print(k4v(edge_attributes, '5.3.1.9'))
## (604, 1037, 0)

The latter code, naively updated replacing iteritems with items, fails to return (604, 3936, 0), (1037, 3936, 0.