understanding csv DictReader, what it returns?-CodePudding

no mind about result of csv.DictReader, so and no possibility to know, are csv params specified correctly.

i have input

Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
sda               0.17        53.98         0.14         0.00   55111129     145632          0
sde               0.14        53.99         0.14         0.00   55118669     147152          0
sdg               0.17        53.99         0.14         0.00   55117853     147076          0

only just spaces are trimmed to one

and that way i want to load it

ios_e = csv.DictReader(' '.join(ios_r.stdout.split()), delimiter = ' ', fieldnames = {'Device', 'tps', 'kB_read/s' ,'kB_wrtn/s', 'kB_dscd/s', 'kB_read', 'kB_wrtn', 'kB_dscd'})

*without specifying fieldnames result is worse, but it should be got by first line? but not

and, for example, I want to work with my Dict:

for v in ios_e.reader:
    for d in v:
        print(d)

and have (there more)

D
e
v
i
c
e


t
p

what i did - you see, what i am shold expect - i don't now I expected matrix-like object, becouse csv like it

what i am get and why?

CodePudding user response：

The csv.DictReader function expects a file object as its first argument, not a string. So, it always is used with normal file io.

for example,

with open('input.csv', 'r') as f:
    reader = csv.DictReader(f, delimiter=' ', fieldnames = ['Device', 'tps', 'kB_read/s' ,'kB_wrtn/s', 'kB_dscd/s', 'kB_read', 'kB_wrtn', 'kB_dscd'])

And, you can iterate the reader (i.e., iterable of dicts) row by row.

for row in reader:
    print(row)

The row variable contains dictionary-like object that you can easily access by key, for example, row['Device'].

CodePudding user response：

The csv module expects the input to be an iterable containing lines of the CSV. ' '.join(ios_r.stdout.split()) is returning a single string (it simply collapses all the whitespace delimiters into single spaces). Iterating over a string returns loops over the characters, not the lines.

You should perform the join and split on each line, not the entire stdout at once.

ios_e = csv.DictReader(' '.join(line.split()) for line in ios_r.stdout, delimiter = ' ')

You won't need the fieldnames argument in this code, since it will get them from the first line.