How can I get a nested dictionary, where both the keys and the subkeys are precisely in the same order as in the csv file?
I tried
import csv
from collections import OrderedDict
filename = "test.csv"
aDict = OrderedDict()
with open(filename, 'r') as f:
csvReader = csv.DictReader(f)
for row in csvReader:
key = row.pop("key")
aDict[key] = row
where test.csv looks like
key,number,letter
eins,1,a
zwei,2,b
drei,3,c
But the sub-dictionaries are not ordered (rows letter and number are changed). So how can I populate aDict[key]
in an ordered manner?
You have to build the dictionaries and sub-dictionaries yourself from rows returned from csv.reader
which are sequences, instead of using csv.DictReader
.
Fortunately that's fairly easy:
import csv
from collections import OrderedDict
filename = 'test.csv'
aDict = OrderedDict()
with open(filename, 'rb') as f:
csvReader = csv.reader(f)
fields = next(csvReader)
for row in csvReader:
temp = OrderedDict(zip(fields, row))
key = temp.pop("key")
aDict[key] = temp
import json # just to create output
print(json.dumps(aDict, indent=4))
Output:
{
"eins": {
"number": "1",
"letter": "a"
},
"zwei": {
"number": "2",
"letter": "b"
},
"drei": {
"number": "3",
"letter": "c"
}
}
This is one way:
import csv
from collections import OrderedDict
filename = "test.csv"
aDict = OrderedDict()
with open(filename, 'r') as f:
order = next(csv.reader(f))[1:]
f.seek(0)
csvReader = csv.DictReader(f)
for row in csvReader:
key = row.pop("key")
aDict[key] = OrderedDict((k, row[k]) for k in order)
csv.DictReader
loads the rows into a regular dict
and not an ordered one. You'll have to read the csv manually into an OrderedDict
to get the order you need:
from collections import OrderedDict
filename = "test.csv"
dictRows = []
with open(filename, 'r') as f:
rows = (line.strip().split(',') for line in f)
# read column names from first row
columns = rows.next()
for row in rows:
dictRows.append(OrderedDict(zip(columns, row)))
You can take advantage of the existing csv.DictReader
class, but alter the rows it returns. To do that, add the following class to the beginning of your script:
class OrderedDictReader(csv.DictReader):
def next(self):
# Get a row using csv.DictReader
row = csv.DictReader.next(self)
# Create a new row using OrderedDict
new_row = OrderedDict(((k, row[k]) for k in self.fieldnames))
return new_row
Then, use this class in place of csv.DictReader
:
csvReader = OrderedDictReader(f)
The rest of your code remains the same.
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