How to skip the headers when processing a csv file using Python?

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I am using below referred code to edit a csv using Python. Functions called in the code form upper part of the code.

Problem: I want the below referred code to start editing the csv from 2nd row, I want it to exclude 1st row which contains headers. Right now it is applying the functions on 1st row only and my header row is getting changed.

in_file = open("tmob_notcleaned.csv", "rb")
reader = csv.reader(in_file)
out_file = open("tmob_cleaned.csv", "wb")
writer = csv.writer(out_file)
row = 1
for row in reader:
    row[13] = handle_color(row[10])[1].replace(" - ","").strip()
    row[10] = handle_color(row[10])[0].replace("-","").replace("(","").replace(")","").strip()
    row[14] = handle_gb(row[10])[1].replace("-","").replace(" ","").replace("GB","").strip()
    row[10] = handle_gb(row[10])[0].strip()
    row[9] = handle_oem(row[10])[1].replace("Blackberry","RIM").replace("TMobile","T-Mobile").strip()
    row[15] = handle_addon(row[10])[1].strip()
    row[10] = handle_addon(row[10])[0].replace(" by","").replace("FREE","").strip()
    writer.writerow(row)
in_file.close()    
out_file.close()

I tried to solve this problem by initializing row variable to 1 but it didn't work.

Please help me in solving this issue.

6

There are 6 answers

4
Martijn Pieters On BEST ANSWER

Your reader variable is an iterable, by looping over it you retrieve the rows.

To make it skip one item before your loop, simply call next(reader, None) and ignore the return value.

You can also simplify your code a little; use the opened files as context managers to have them closed automatically:

with open("tmob_notcleaned.csv", "rb") as infile, open("tmob_cleaned.csv", "wb") as outfile:
   reader = csv.reader(infile)
   next(reader, None)  # skip the headers
   writer = csv.writer(outfile)
   for row in reader:
       # process each row
       writer.writerow(row)

# no need to close, the files are closed automatically when you get to this point.

If you wanted to write the header to the output file unprocessed, that's easy too, pass the output of next() to writer.writerow():

headers = next(reader, None)  # returns the headers or `None` if the input is empty
if headers:
    writer.writerow(headers)
0
bitbang On

Simply iterate one time with next()

with open(filename) as file:

    csvreaded = csv.reader(file)
    header = next(csvreaded)

    for row in csvreaded:
        empty_list.append(row) #your csv list without header  

or use [1:] at the end of reader object

with open(filename) as file:

    csvreaded = csv.reader(file)
    header = next(csvreaded)

    for row in csvreaded[1:]:
        empty_list.append(row) #your csv list without header  
3
Chad Zawistowski On

Another way of solving this is to use the DictReader class, which "skips" the header row and uses it to allowed named indexing.

Given "foo.csv" as follows:

FirstColumn,SecondColumn
asdf,1234
qwer,5678

Use DictReader like this:

import csv
with open('foo.csv') as f:
    reader = csv.DictReader(f, delimiter=',')
    for row in reader:
        print(row['FirstColumn'])  # Access by column header instead of column number
        print(row['SecondColumn'])
0
oaklodge On
with open(filename, 'r') as file:
    reader = csv.DictReader(file, fieldnames=None)
    # for some reason fieldnames=None causes first row to be skipped
    for row in reader: 
        print(row) # so the the first row printed is second row in file
3
Darío López Padial On

Inspired by Martijn Pieters' response.

In case you only need to delete the header from the csv file, you can work more efficiently if you write using the standard Python file I/O library, avoiding writing with the CSV Python library:

with open("tmob_notcleaned.csv", "rb") as infile, open("tmob_cleaned.csv", "wb") as outfile:
   next(infile)  # skip the headers
   outfile.write(infile.read())
2
Katriel On

Doing row=1 won't change anything, because you'll just overwrite that with the results of the loop.

You want to do next(reader) to skip one row.