DictReader와 DictWriter를 사용하여 Python에서 CSV를 유연하게 처리

The code in this article is also available in a public Github repo here.

Last name,First name,Middle name,Role,School,Grade
Herman,Preston,Elliott,Teacher,Southside,
Randolph,Finnegan,Braylon,Student,Eastside,12
Hood,Easton,Fernando,Student,Southside,7
Kemp,Logan,Kinsley,Teacher,Southside,

from pathlib import Path

inpath = Path("sample.csv")

with inpath.open("r") as infile:
    contents = infile.read()

Admittedly, it would be even easier to write contents = inpath.read_text(). However, that would not have demonstrated with and open very well! And it isn't relevant for CSV handling, as you will see in the next sentence.

import csv
from pathlib import Path


inpath = Path("sample.csv")

with inpath.open("r", newline="", encoding="utf-8-sig") as infile:
    reader = csv.DictReader(infile)
    for row in reader:
        fullname= f"{row['First name']} {row['Middle name']} {row['Last name']}"
        print(fullname)

$ python simplereader.py
Preston Elliott Herman
Finnegan Braylon Randolph
Easton Fernando Hood
Logan Kinsley Kemp

Depending on your system, you may need to use python3 instead of python. If python -V doesn't show something like Python 3.8.5 (the 3 is the important part!), and python3 -V does, then use the latter instead.

import csv
from pathlib import Path


outpath = Path("out/output.csv")
outpath.parent.mkdir(exist_ok=True)  # ensure the "out" directory exists

with outpath.open("w", newline="", encoding="utf-8-sig") as outfile:
    writer = csv.DictWriter(outfile, ["First", "Last"])
    writer.writeheader()
    new_row = {"First": "Jane", "Last": "Smith"}
    writer.writerow(new_row)

inpath = Path("sample.csv")
outpath = Path("out/transformed.csv")
args = {"newline": "", "encoding": "utf-8-sig"}
with inpath.open("r", **args) as infile, outpath.open("w", **args) as outfile:
    reader = csv.DictReader(infile)
    writer = csv.DictWriter(outfile, ["Firstname", "Lastname", "Username"])

import csv
from pathlib import Path


def transform():
    """Filters and transforms each row of input CSV, with output to a separate file."""
    inpath = Path("sample.csv")
    outpath = Path("out/transformed.csv")
    outpath.parent.mkdir(exist_ok=True)
    args = {"newline": "", "encoding": "utf-8-sig"}
    with inpath.open("r", **args) as infile, outpath.open("w", **args) as outfile:
        reader = csv.DictReader(infile)
        writer = csv.DictWriter(outfile, ["Firstname", "Lastname", "Username"])

        writer.writeheader()

        for row in reader:
            if row["Role"] == "Student":
                new_row = {
                    "Firstname": row["First name"],
                    "Lastname": row["Last name"],
                    "Username": f"{row['Last name']}{row['First name']}".lower(),
                }
                writer.writerow(new_row)


if __name__ == "__main__":
    transform()

"""Python CSV handling demo."""

__version__ = "0.1.0"

import argparse
import csv
import sys
from pathlib import Path


def transform(
    infilename, outfilename, inencoding="utf-8-sig", outencoding="utf-8-sig",
):
    """Filters and transforms each row, with output to a separate file."""
    inpath = Path(infilename)
    outpath = Path(outfilename)
    args = {"newline": ""}
    inargs = {"encoding": inencoding, **args}
    outargs = {"encoding": outencoding, **args}
    with inpath.open("r", **inargs) as infile, outpath.open("w", **outargs) as outfile:
        reader = csv.DictReader(infile)
        writer = csv.DictWriter(outfile, ["Firstname", "Lastname", "Username"])

        writer.writeheader()

        for row in reader:
            if row["Role"] == "Student":
                new_row = {
                    "Firstname": row["First name"],
                    "Lastname": row["Last name"],
                    "Username": f"{row['Last name']}{row['First name']}".lower(),
                }
                writer.writerow(new_row)


def run(args=None):
    """Execute as command line script."""
    if not args:
        args = sys.argv[1:]
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "inputfile", help="read from this CSV file",
    )
    parser.add_argument(
        "outputfile", help="save to this CSV file",
    )
    parser.add_argument(
        "-e",
        "--encoding",
        default="utf-8-sig",
        help="character encoding of input and output files",
    )
    parser.add_argument(
        "-ie", "--inputencoding", help="character encoding of input file",
    )
    parser.add_argument(
        "-oe", "--outputencoding", help="character encoding to use for output file",
    )
    args = parser.parse_args(args)

    inputencoding = args.inputencoding or args.encoding
    outputencoding = args.outputencoding or args.encoding

    transform(args.inputfile, args.outputfile, inputencoding, outputencoding)


if __name__ == "__main__":
    run()

python csvdemo.py -e utf-8-sig sample.csv out/sample_transformed.csv

python csvdemo.py -ie utf-8-sig -oe cp1252 sample.csv out/sample_transformed_western.csv