Write dictionary to file (CSV or TSV) where key is multiple items

Question

How do I write a dictionary to a CSV or TSV when my data looks like this (multiple items in key):

defaultdict(<type 'list'>, {('1_719263', 35, 4): [(1, 1, 'KEEP')]})

where the key is ('1_713', 35, 4) and the value is [(1, 1, 'KEEP')].

I wanted to use json or even csv.writer.

I have also tried this:

with open (output_name, "a") as f:
    f.write(first_line + "\n")
    for key, value in x_y_output.iteritems():
        f.write(str((key, value)) + "\n")

But this does not work and I cannot get rid of the (), [], {}, etc.

Answer 1

You could try formatting your output string as a TAB separated line:

with open (output_name, "a") as f:
    f.write(first_line + "\n")
    for key, value in my_dict.items():
        f.write("{}\t{}\n".format(key, value))

Then when reading in data, you could reconstruct it using:

new_dict = {}
with open (output_name, "r") as f:
    for line in f:
        inline_list = line.rstrip.split('\t')
        new_dict[eval(inline_list[0])] = eval(inline_list[1])

Examples in python shell:

>>> src_dict
{('1_719263', 35, 4): [(1, 1, 'KEEP')]}
>>> for key, value in d.items():
...     outstring = "{}\t{}\n".format(k,v)
...     # write to file
... 
>>> outstring
"('1_719263', 35, 4)\t[(1, 1, 'KEEP')]\n"
>>> instring = outstring.rstrip().split('\t')
>>> instring
["('1_719263', 35, 4)", "[(1, 1, 'KEEP')]"]
>>> new_dict = {}
>>> new_dict[eval(instring[0])] = eval(instring[1])
>>> new_dict
{('1_719263', 35, 4): [(1, 1, 'KEEP')]}