Finding Blank Columns in CSV

[Chris Angelico]

On Tue, Oct 6, 2015 at 12:29 AM, Jaydip Chakrabarty
<chalao.adda at gmail.com> wrote:
> I want to find out the blank columns, that is, fields where all the
> values are blank. Here is my python code.
>
> fn = "tmp1.csv"
> fin = open(fn, 'rb')
> rdr = csv.DictReader(fin, delimiter=',')
> data = list(rdr)
> flds = rdr.fieldnames
> fin.close()
> mt = []
> flag = 0
> for i in range(len(flds)):
>     for row in data:
>         if len(row[flds[i]]):
>             flag = 0
>             break
>         else:
>             flag = 1
>     if flag:
>         mt.append(flds[i])
>         flag = 0
> print mt
>
> I need to know if there is better way to code this.
>

You could do it with a single iteration, something like this:

fn = "tmp1.csv"
fin = open(fn, 'rb')
rdr = csv.DictReader(fin, delimiter=',')
# all the same down to here
blanks = set(rdr.fieldnames)
for row in data:
    blanks = {col for col in blanks if not row[col]}
mt = [col for col in rdr.fieldnames if col not in blanks]
print mt