How to add new column(header) to a csv file from command line arguments

Question

The output of the following code:-

import datetime
import csv
file_name='sample.txt'
with open(file_name,'rb') as f:               
    reader = csv.reader(f,delimiter=",")                                              
    #headers = reader.next()
    p=[]
    for row in reader:

        row[0] = row[0].zfill(6) 
        row[2] = row[2].zfill(6)
        row[3] = row[3].zfill(6)
        row[4] = row[4].zfill(6)
        row[1] = row[1][5:7] + "-" + row[1][8:10] + "-" + row[1][:4]
        p.append(row[:5])
        print p
with open('names.txt', 'wb') as ofile:
    writer = csv.writer(ofile)
    for row in p:
        writer.writerow(row)

is following:-

User_ID,--Date,0Num_1,0Num_2,Com_ID
000101,04-13-2015,000012,000021,001011
000102,04-03-2014,000001,000007,001002
000103,06-05-2013,000003,000004,000034
000104,12-31-2012,000004,000009,001023
000105,09-09-2011,000009,000005,000104

I want to add a new column to the csv file from command line. e.g. python script_name.py Dept_ID Location will create columns for Dept_ID and Location next to Comp_ID.

Can any one guide me here please!

possible duplicate of [Pythonically add header to a csv file](http://stackoverflow.com/questions/20347766/pythonically-add-header-to-a-csv-file) — Alexander McFarlane, Jun 05 '15 at 04:20
For command line options take a look at getopt. https://docs.python.org/2/library/getopt.html — haronaut, Jun 05 '15 at 04:23

score 2 · Accepted Answer · edited May 23 '17 at 12:22

see this post which suggests something like the following:

header = ['User_ID','--Date','0Num_1','0Num_2','Com_ID']
writer = csv.DictWriter(outcsv, fieldnames = header)
writer.writeheader()
writer.writerows({col: row} for row, col in zip(header, p))

to parse the extra columns from the system arguments use sys.argv

import sys

extra_headers = sys.argv
header.extend(sys.argv)
n = len(sys.argv)

writer = csv.DictWriter(outcsv, fieldnames = header)
writer.writeheader()

col_fill = ''
# extend p with two columns of blank data
writer.writerows({col: row_item} for row in p for row_item,col in zip(row+[col_fill]*n,header))

here I iterate through each row, I then crate a dictionary to allocate data to each column in order. Notice [col_fill]*n this creates a list of identical items equal to col_fill that will be used to fill the additional columns parsed in via command line arguments.

In this example the command line arguments would be parsed as:

$ python script_name.py Dept_ID Location

and would create:

User_ID,--Date,0Num_1,0Num_2,Com_ID,Dept_ID,Location
000101,04-13-2015,000012,000021,001011,,
000102,04-03-2014,000001,000007,001002,,
000103,06-05-2013,000003,000004,000034,,
000104,12-31-2012,000004,000009,001023,,
000105,09-09-2011,000009,000005,000104,,

score 0 · Answer 2 · answered Jun 05 '15 at 04:44

you can use sys.argv to get arguments from command line.

import sys

print 'Number of arguments:', len(sys.argv), 'arguments.'
print 'Argument List:', str(sys.argv)

$ python script_name.py Dept_ID Location

Number of arguments: 4 arguments.
Argument List: ['script_name.pyy', 'Dept_ID Locatio']

after you get the argument from command line, you could add it into your file

How to add new column(header) to a csv file from command line arguments

2 Answers2

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