Adding items to a nested dictionary

Question

I am trying to read a list within a list and add keys and values to a dictionary within a dictionary. But I get the 'str' object doesn't support assignment error.

Code:

report_dict = dict()
axis_list = []
results = self.report_data(conn)
for row in results:
  try:
    report_dict[row[0]] = row[3]
    report_dict[row[0]][row[3]] = row[1]
  except IndexError:
    None 
  print(report_dict)

Result:

report_dict = { abc: {qwe:asd}, …..}

@qwerty I think @Wondercricket meant the results variable in your code, not the desired result of your code. — schneebuzz
– schneebuzz, Commented Feb 13, 2020 at 15:00
Its just a list within a list. So essentially row is a list from which I am inputting abc, qwe,asd into the dictionary — qwerty
– qwerty, Commented Feb 13, 2020 at 15:02

CDJB · Accepted Answer · 2020-02-13 15:00:42Z

2

I think what you're trying to do is make a nested dictionary. If I understand your input correctly, your code could be fixed just by setting report_dict[row[0]] to an empty dict, by changing

report_dict[row[0]] = row[3]

to

report_dict[row[0]] = {}

This would make the next line,

report_dict[row[0]][row[3]] = row[1]

add the key row[3] with value row[1] to the dictionary report_dict[row[0]]. This would give us:

report_dict = {row[0]: {row[3]: row[1]}, ...}

which I think is your expected output.

answered Feb 13, 2020 at 15:00

CDJB

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5 Comments

qwerty Over a year ago

report_dict[row[0]] = {} in the for loop, wont it cause the data to be overwritten if the first key is same? Check the expected result.

CDJB Over a year ago

@qwerty yes, you can't have duplicate keys in a dictionary. Please ask your new requirements in a new question rather than editing this answered question!

qwerty Over a year ago

Okay, what would you do for duplicated keys, append it to another dictionary?

CDJB Over a year ago

@qwerty depends what you want your data structure to be?

qwerty Over a year ago

end of the day it should be a dictionary.

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