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Subject: Re: Finding Blank Columns in CSV
To: python-list@python.org
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Date: Mon, 5 Oct 2015 22:08:33 +0200
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On 10/05/2015 03:29 PM, Jaydip Chakrabarty wrote:
> Hello,
>
> I have a csv file like this.
>
> Name,Surname,Age,Sex
> abc,def,,M
> ,ghi,,F
> jkl,mno,,
> pqr,,,F
>
> 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.
>
> Thanks.
>
Operations on columns are often simpler, if a table is rotated 
beforehand. Columns become lists.

def find_empty_columns (table):
     number_of_records = len (table)
     rotated_table = zip (*table)
     indices_of_empty_columns = []
     for i in range (len (rotated_table)):  # Column indices
         if rotated_table[i].count ('') == number_of_records:
             indices_of_empty_columns.append (i)
     return indices_of_empty_columns

Frederic