How to delete columns in a CSV file

Question

I have been able to create a csv with python using the input from several users on this site and I wish to express my gratitude for your posts   I am now stumped and will post my first question   My input csv looks like this   day month year lat long 01 04 2001 45 00 120 00 02 04 2003 44 00 118 00   I am trying to delete the  year  column and all of its entries   In total there is 40  entries with a range of years from 1960-2010

User · Answer

It depends on how you store the parsed CSV, but generally you want the del operator.

If you have an array of dicts:

input = [ {'day':01, 'month':04, 'year':2001, ...}, ... ]
for E in input: del E['year']

If you have an array of arrays:

input = [ [01, 04, 2001, ...],
          [...],
          ...
        ]
for E in input: del E[2]

User · Answer

Use of Pandas module will be much easier   import pandas as pd f pd read csv  test csv   keep col     day   month   lat   long   new f   f keep col  new f to csv  newFile csv   index False    And here is short explanation    gt  gt  gt f pd read csv  test csv    gt  gt  gt  f    day  month  year  lat  long 0    1      4  2001   45   120 1    2      4  2003   44   118  gt  gt  gt  keep col     day   month   lat   long     gt  gt  gt  f keep col      day  month  lat  long 0    1      4   45   120 1    2      4   44   118  gt  gt  gt

User · Answer

I would use Pandas with col number  f   pd read csv  test csv   usecols  0 1 3 4    f to csv  test csv   index False

User · Answer

You can directly delete the column with just  del variable name  year

User · Answer

Try    result  data drop  year   1  result head 5

User · Answer

Off the top of my head  this will do it without any sort of error checking nor ability to configure anything  That is  left to the reader    outFile   open   newFile    w    for line in open   oldFile        items   line split           outFile write      join  items  2    items  3        outFile close

User · Answer

Using a dict to grab headings then looping through gets you what you need cleanly   import csv ct   0 cols i want     cost    -1   date    -1  with open  file1 csv   rb   as source      rdr   csv reader  source       with open  result   wb   as result          wtr   csv writer  result           for row in rdr              if ct    0                cc   0               for col in row                  for ciw in cols i want                     if col    ciw                      cols i want ciw    cc                 cc    1             wtr writerow   row cols i want  cost     row cols i want  date                   ct    1

User · Answer

import csv with open  source   rb   as source      rdr  csv reader  source       with open  result   wb   as result          wtr  csv writer  result           for r in rdr              wtr writerow   r 0   r 1   r 3   r 4       BTW  the for loop can be removed  but not really simplified           in iter     r 0   r 1   r 3   r 4   for r in rdr           wtr writerows  in iter     Also  you can stick in a hyper-literal way to the requirements to delete a column   I find this to be a bad policy in general because it doesn t apply to removing more than one column   When you try to remove the second  you discover that the positions have all shifted and the resulting row isn t obvious   But for one column only  this works               del r 2              wtr writerow  r

User · Answer

you can use the csv package to iterate over your csv file and output the columns that you want to another csv file   The example below is not tested and should illustrate a solution   import csv  file name    C  Temp my file csv  output file    C  Temp new file csv  csv file   open file name   r      note that the index of the year column is excluded column indices    0 1 3 4  with open output file   w   as fh      reader   csv reader csv file  delimiter          for row in reader         tmp row             for col inx in column indices             tmp row append row col inx          fh write     join tmp row

[python] How to delete columns in a CSV file?

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