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, Jun 16 '17 at 16:12
I've added content if it helps. I'll make changes to split as well — Jaron787, Jun 16 '17 at 16:18

Prune · Answer 1 · 2017-06-16T16:33:58.723

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 '17 at 16:33

answered Jun 16 '17 at 16:28

Prune

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score 1 · Accepted Answer · answered Jun 16 '17 at 16:36

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(',')

Python append multiple values to nested dictionary by key

2 Answers2

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