Python Dictreader Sorting Fieldnames

Question

I have a .csv file with the content (example)

Attributes,Description,Dial-Up
4,2,0.2
3,1,0.4

Using the dictreader:

dictreader = csv.DictReader(open(filename, "rb"), delimiter=',')
dictdata = {}
count=0
for row in dictreader:
    dictdata[count]=row
    count=count+1

And display in table or using writer i will get:

Dial-Up,Attributes,Description
0.2,4,2
0.4,3,1

So how can i sort the fieldnames?

Answer 1

The DictReader stores the fields (dict keys) in an property called fieldnames:

fields = dictreader.fieldnames
print(fields)
# ['Attributes', 'Description', 'Dial-Up']

So to print the row values in this order:

print(','.join(fields))
for row in dictreader:
    print(','.join(row[field] for field in fields))

yields

Attributes,Description,Dial-Up
4,2,0.2
3,1,0.4

---

Or, using @JonClements' idea:

import operator
fields = dictreader.fieldnames
getfields = operator.itemgetter(*fields)
for row in dictreader:
    print(','.join(getfields(row)))

The motivation for using operator.itemgetter would be that it is faster than using a list comprehension:

In [70]: %timeit getfields(row)
10000000 loops, best of 3: 174 ns per loop

In [71]: %timeit [row[field] for field in fields]
1000000 loops, best of 3: 272 ns per loop