Python append multiple values to nested dictionary by key

Question

I am trying to add another value to a nested dictionary by key, I have the below code but it doesn't work properly

Content is a file with:
a,b,c,d
a,b,c,d
a,b,c,d

dict   = {}

for line in content:
    values = line.split(",")
    a = str.strip(values[0])
    b = str.strip(values[1])
    c = str.strip(values[2])
    d = str.strip(values[3])

    if a not in dict:
        dict.update({a: {'Value1': b, 'Value2': c, 'Value3': d}},)
    else:
       dict[a]['Value1'].update(b)

I want it to look like:

a {'Value1': 'b,b,b', 'Value2': 'c', 'Value3': 'd'}

What am I doing wrong?

Not a big deal, but you can probably write a, b, c, d = [x.strip() for x in line.split()] so it looks more pythonic :) — Bubble Bubble Bubble Gut
– Bubble Bubble Bubble Gut, Commented Jun 16, 2017 at 16:12
I've added content if it helps. I'll make changes to split as well — Jaron787
– Jaron787, Commented Jun 16, 2017 at 16:18

Prune · Accepted Answer · 2017-06-16 16:33:58Z

2

You don't quite understand with update does; it's replacement, not appending. Try this, instead:

if a not in dict:
    dict.update({a: {'Value1': b, 'Value2': c, 'Value3': d}},)
else:
   dict[a]['Value1'] += ',' + b

Output:

a {'Value3': 'd', 'Value2': 'c', 'Value1': 'b,b,b'}

If you want to preserve the order of the Value sub-fields, then use an OrderedDict.

edited Jun 16, 2017 at 16:33

answered Jun 16, 2017 at 16:28

Prune

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Comments

Gabriel Belini · Accepted Answer · 2017-06-16 16:36:37Z

1

dictionary = {}

for line in content: 
  values = line.split(",")
  a = str.strip(values[0])
  b = str.strip(values[1])
  c = str.strip(values[2])
  d = str.strip(values[3])

  if a not in dictionary.keys():
      dictionary = {a: {'Value1': b, 'Value2': c, 'Value3': d}} # creates dictionary
  else:
      dictionary[a]['Value1'] += ','+b # accesses desired value and updates it with ",b"
print(dictionary)
#Output: {'a': {'Value1': 'b,b,b', 'Value2': 'c', 'Value3': 'd'}}

This should do your trick. You gotta add the ',' in the else statement because you removed it when you used split(',')

answered Jun 16, 2017 at 16:36

Gabriel Belini

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