Trying to combine three columns in CSV and then updating the original CSV file

Question

Trying to combine three columns in CSV and then updating the original CSV file

Here is some sample data:

name1|name2|name3|name4|combined
test|data|here|and
test|information|343|AND
",3|record|343|and

My coding solution:

import csv
import StringIO

storedoutput = StringIO.StringIO()
fields = ('name1', 'name2', 'name3', 'name4', 'combined')
with open('file.csv', 'rb') as input_csv:
    reader = csv.DictReader(input_csv, fields, delimiter='|')
    for counter, row in enumerate(reader):
        counter += 1
        #print row
        if counter != 1:
            for field in fields:
                if field == "combined":
                    row['combined'] = ("%s%s%s" % (row["name1"], row["name3"], row["name4"]))
                    print row
                    storedoutput.writelines(','.join(map(str, row)) + '\n')

contents = storedoutput.getvalue()
storedoutput.close()

print "".join(contents)

with open('file.csv', 'rb') as input_csv:
    input_csv = input_csv.read().strip()

output_csv = []
output_csv.append(contents.strip())

if "".join(output_csv) != input_csv:
    with open('file.csv', 'wb') as new_csv:
        new_csv.write("".join(output_csv))

The expected output:

name1|name2|name3|name4|combined
test|data|here|and|testhereand
test|information|343|AND|test343AND
",3|record|343|and|",3343and

When this code runs, the first print statement displays the rows as intended in the output CSV. However, the second print statement repeats the title row multiple times, equal to the number of rows.

We welcome any feedback, corrections, or functional code examples from you.

python python-2.7 csv

Answer 1

Answer №1

I believe we have the opportunity to simplify this process significantly. Handling the stray " character proved to be a bit of a challenge, as Python requires some effort to disregard it.

import csv

with open('file.csv', 'rb') as input_csv, open("new_file.csv", "wb") as output_csv:
    reader = csv.DictReader(input_csv, delimiter='|', quoting=csv.QUOTE_NONE)
    writer = csv.DictWriter(output_csv, reader.fieldnames, delimiter="|",quoting=csv.QUOTE_NONE, quotechar=None)

    merge_cols = "title1", "title3", "title4"

    writer.writeheader()

    for row in reader:
        row["merge"] = ''.join(row[col] for col in merge_cols)
        writer.writerow(row)

resulting in

$ cat new_file.csv 
title1|title2|title3|title4|merge
test|data|here|and|testhereand
test|data|343|AND|test343AND
",3|data|343|and|",3343and

Please note that despite your request to update the original file, I declined. Why? Making changes directly to the source file can lead to data loss and corruption during manipulation.

How am I so certain? Because that was my initial misstep when running your code for the first time, but now I've learned from it. ;^)

Answer 2

I believe we have the opportunity to simplify this process significantly. Handling the stray " character proved to be a bit of a challenge, as Python requires some effort to disregard it.

import csv

with open('file.csv', 'rb') as input_csv, open("new_file.csv", "wb") as output_csv:
    reader = csv.DictReader(input_csv, delimiter='|', quoting=csv.QUOTE_NONE)
    writer = csv.DictWriter(output_csv, reader.fieldnames, delimiter="|",quoting=csv.QUOTE_NONE, quotechar=None)

    merge_cols = "title1", "title3", "title4"

    writer.writeheader()

    for row in reader:
        row["merge"] = ''.join(row[col] for col in merge_cols)
        writer.writerow(row)

resulting in

$ cat new_file.csv 
title1|title2|title3|title4|merge
test|data|here|and|testhereand
test|data|343|AND|test343AND
",3|data|343|and|",3343and

Please note that despite your request to update the original file, I declined. Why? Making changes directly to the source file can lead to data loss and corruption during manipulation.

How am I so certain? Because that was my initial misstep when running your code for the first time, but now I've learned from it. ;^)

Answer 3

Answer №2

The quotation mark at the end of the previous sentence appears to be causing some issues with the csv.DictReader(). The following solution seems to work well:

fresh_lines = []
with open('data.csv', 'rb') as file:
    # skip over the first line
    fresh_lines.append(file.next().strip())
    for row in file:
        # remove any extra spaces and split up the fields
        row = row.strip().split('|')
        # extract the specific field information needed
        info1, info3, info4 = row[0], row[2], row[3]
        # combine the extracted data into a single string and add it back to the rest
        row.append(''.join([info1, info3, info4]))
        # store the updated row for later use
        fresh_lines.append('|'.join(row))

with open('data.csv', 'w') as file:
    # concatenate all lines into one long string and write it to the new file
    file.write('\n'.join(fresh_lines))

Answer 4

The quotation mark at the end of the previous sentence appears to be causing some issues with the csv.DictReader(). The following solution seems to work well:

fresh_lines = []
with open('data.csv', 'rb') as file:
    # skip over the first line
    fresh_lines.append(file.next().strip())
    for row in file:
        # remove any extra spaces and split up the fields
        row = row.strip().split('|')
        # extract the specific field information needed
        info1, info3, info4 = row[0], row[2], row[3]
        # combine the extracted data into a single string and add it back to the rest
        row.append(''.join([info1, info3, info4]))
        # store the updated row for later use
        fresh_lines.append('|'.join(row))

with open('data.csv', 'w') as file:
    # concatenate all lines into one long string and write it to the new file
    file.write('\n'.join(fresh_lines))

Answer 5

Answer №3

import csv
import StringIO

stored_output = StringIO.StringIO()

with open('data.csv', 'rb') as input_csv:
    reader = csv.DictReader(input_csv, delimiter='|', quoting=csv.QUOTE_NONE)
    writer = csv.DictWriter(stored_output, reader.fieldnames, delimiter="|",quoting=csv.QUOTE_NONE, quotechar=None)

    merge_columns = "name", "age", "city"

    writer.writeheader()

    for row in reader:
        row["merge"] = ''.join(row[col] for col in merge_columns)
        writer.writerow(row)

    new_data = stored_output.getvalue()
    stored_output.close()
    print new_data

with open('data.csv', 'rb') as input_csv:
    input_contents = input_csv.read().strip()

if input_contents != new_data.strip():
    with open('data.csv', 'wb') as updated_csv:
        updated_csv.write("".join(new_data))

Answer 6

import csv
import StringIO

stored_output = StringIO.StringIO()

with open('data.csv', 'rb') as input_csv:
    reader = csv.DictReader(input_csv, delimiter='|', quoting=csv.QUOTE_NONE)
    writer = csv.DictWriter(stored_output, reader.fieldnames, delimiter="|",quoting=csv.QUOTE_NONE, quotechar=None)

    merge_columns = "name", "age", "city"

    writer.writeheader()

    for row in reader:
        row["merge"] = ''.join(row[col] for col in merge_columns)
        writer.writerow(row)

    new_data = stored_output.getvalue()
    stored_output.close()
    print new_data

with open('data.csv', 'rb') as input_csv:
    input_contents = input_csv.read().strip()

if input_contents != new_data.strip():
    with open('data.csv', 'wb') as updated_csv:
        updated_csv.write("".join(new_data))

Trying to combine three columns in CSV and then updating the original CSV file

Here is some sample data:

My coding solution:

The expected output:

Answer №1

Answer №2

Answer №3

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