How to Create Nested Dict in Python

How do you create nested dict in Python?

A nested dict is a dictionary within a dictionary. A very simple thing.

>>> d = {}
>>> d['dict1'] = {}
>>> d['dict1']['innerkey'] = 'value'
>>> d['dict1']['innerkey2'] = 'value2'
>>> d
{'dict1': {'innerkey': 'value', 'innerkey2': 'value2'}}

You can also use a defaultdict from the collections package to facilitate creating nested dictionaries.

>>> import collections
>>> d = collections.defaultdict(dict)
>>> d['dict1']['innerkey'] = 'value'
>>> d  # currently a defaultdict type
defaultdict(<type 'dict'>, {'dict1': {'innerkey': 'value'}})
>>> dict(d)  # but is exactly like a normal dictionary.
{'dict1': {'innerkey': 'value'}}

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You can populate that however you want.

I would recommend in your code something like the following:

d = {}  # can use defaultdict(dict) instead

for row in file_map:
    # derive row key from something 
    # when using defaultdict, we can skip the next step creating a dictionary on row_key
    d[row_key] = {} 
    for idx, col in enumerate(row):
        d[row_key][idx] = col

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According to your comment:

may be above code is confusing the question. My problem in nutshell: I
have 2 files a.csv b.csv, a.csv has 4 columns i j k l, b.csv also has
these columns. i is kind of key columns for these csvs'. j k l column
is empty in a.csv but populated in b.csv. I want to map values of j k
l columns using 'i` as key column from b.csv to a.csv file

My suggestion would be something like this (without using defaultdict):

a_file = "path/to/a.csv"
b_file = "path/to/b.csv"

# read from file a.csv
with open(a_file) as f:
    # skip headers
    f.next()
    # get first colum as keys
    keys = (line.split(',')[0] for line in f) 

# create empty dictionary:
d = {}

# read from file b.csv
with open(b_file) as f:
    # gather headers except first key header
    headers = f.next().split(',')[1:]
    # iterate lines
    for line in f:
        # gather the colums
        cols = line.strip().split(',')
        # check to make sure this key should be mapped.
        if cols[0] not in keys:
            continue
        # add key to dict
        d[cols[0]] = dict(
            # inner keys are the header names, values are columns
            (headers[idx], v) for idx, v in enumerate(cols[1:]))

Please note though, that for parsing csv files there is a csv module.

How to create a nested dictionary in python with 6 lists

Maybe something like:

out = {k: {k1: v1, k2: v2} for k, k1, v1, k2, v2 in zip(a, b, c, d, e)}

If we want to use excessive number of zips, we could also do:

out = {k: dict(v) for k,v in zip(a, zip(zip(b, c), zip(d, e)))}

Output:

{'A':{1 :9, 0:11} , 'B':{2:8, 3:13}, 'C':{3:7, 5:13} , 'D':{4:6, 7:15}}

How to create nested dictionaries PYTHON

Use a list comprehension. Iterate over the zipped lists and create the nested dictionaries:

a = ['A', 'B', 'C', 'D']
b = [1, 2, 3, 4]
c = ['N1', 'N2', 'N3', 'N4']

>>> [{k1: {k2: v}} for k1, v, k2 in zip(a, b, c)]
[{'A': {'N1': 1}}, {'B': {'N2': 2}}, {'C': {'N3': 3}}, {'D': {'N4': 4}}]

How to create a nested dictionary from a list of lists

Here is a solution you can give it a try,

print({
    k: v for k, v in enumerate(dict(zip(val[0], v)) for v in val[1:])
})

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{0: {'a': 1, 'b': 'a', 'c': 'x'}, 1: {'a': 2, 'b': 'b', 'c': 'y'}}

Create a nested Dictionary with two dictionaries

You can use defaultdict here. multi need not be sorted.

from collections import defaultdict
out=defaultdict(dict)
for v,k,vs in multi:
    out[k]={**out[k],**{v:vs[0]}}

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Output

defaultdict(dict,
            {77766: {14: 2, 15: 1},
             88866: {70: 1, 71: 2, 72: 5, 73: 4, 74: 3},
             99966: {79: 1, 80: 2}})

EDIT:

Sorting the inner dictionaries.

out={k:dict(sorted(v.items(),key=lambda x:x[1])) for k,v in out.items()}

Output:

{77766: {15: 1, 14: 2},
 88866: {70: 1, 71: 2, 74: 3, 73: 4, 72: 5},
 99966: {79: 1, 80: 2}}

Create nested dictionary from directory

instead of using the assignment operator here:

dict[key] = {x[:-4]: {'path': f'database/{x}'}}

call the update method on the dictionary:

dict[key].update({x[:-4]:{'path': f'database/{x}'}})

Create nested dictionary with same keys from a file

d = {}

for line in file:
    line = line.rstrip()
    department, name, cre = line.split(',')

    if department not in d:
        d[department] = {}

    d[department][name] = cre

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