Use argparse in merge_csv.py.

# See the License for the specific language governing permissions and

# limitations under the License.

"""

Merge mutliple CSV files, possibly with different columns, writing to stdout.

Merge multiple CSV files, possibly with different columns.

"""

import argparse

import csv

import sys

import io

csv_readers = [

    csv.DictReader(open(csv_file, 'r'), delimiter=',', quotechar='|')

    for csv_file in sys.argv[1:]

]

from zipfile import ZipFile

args_parser = argparse.ArgumentParser(description='Merge given CSV files into a single one.')

args_parser.add_argument('--header', help='Comma separated field names; '

                                          'if missing determines the header from input files.')

args_parser.add_argument('--zip_input', help='ZIP archive with all CSV files to merge.')

args_parser.add_argument('--output', help='Output file for merged CSV.',

                         default='-', type=argparse.FileType('w'))

args_parser.add_argument('files', nargs=argparse.REMAINDER)

args = args_parser.parse_args()

def dict_reader(input):

    return csv.DictReader(input, delimiter=',', quotechar='|')

if args.zip_input and len(args.files) > 0:

    raise ValueError('Expecting either a single ZIP with CSV files'

                     ' or a list of CSV files as input; not both.')

csv_readers = []

if len(args.files) > 0:

    for file in args.files:

        csv_readers.append(dict_reader(open(file, 'r')))

elif args.zip_input:

    with ZipFile(args.zip_input) as zip:

        for entry in zip.namelist():

            if entry.endswith('.uau'):

                csv_readers.append(dict_reader(io.TextIOWrapper(zip.open(entry, 'r'))))

# Build union of all columns from source files:

headers = set()

if args.header:

    fieldnames = args.header.split(',')

else:

    # Build union of all columns from source files:

    for reader in csv_readers:

        headers = headers.union(reader.fieldnames)

    fieldnames = sorted(headers)

# Concatenate all files to output:

out = csv.DictWriter(sys.stdout, delimiter=',', quotechar='|', quoting=csv.QUOTE_MINIMAL,

                     dialect='unix', fieldnames=sorted(headers))

out.writeheader()

writer = csv.DictWriter(args.output, delimiter=',', quotechar='|', quoting=csv.QUOTE_MINIMAL,

                        dialect='unix', fieldnames=fieldnames)

writer.writeheader()

for reader in csv_readers:

    for row in reader:

        out.writerow(row)

        writer.writerow(row)