Try to autodetect and display CSV or TSV data in a terminal. Fall back to plain text if auto detection fails.

csv-display.py

#! /usr/bin/env python3

"""Try to autodetect, parse and display CSV, but fallback to plain text otherwise."""

# Copyright 2024 Fredrik Mellström <https://github.com/harkabeeparolus>
# MIT License; SPDX short identifier: MIT

import argparse
import csv
import io
import itertools as it
import sys
from contextlib import suppress
from pathlib import Path


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument(
        "-a",
        "--any-delimiter",
        action="store_true",
        help="consider any character as a delimiter (default: ,;: and <tab>)",
    )
    parser.add_argument(
        "-c", "--out-csv", action="store_true", help="output well-formed, standard CSV"
    )
    parser.add_argument("input_file", nargs="?")
    args = parser.parse_args()

    if sys.stdin.isatty() and not args.input_file:
        parser.error("No input file specified.")
    if args.input_file and not Path(args.input_file).is_file():
        parser.error(f"Invalid file: {args.input_file}")

    try:
        if args.input_file:
            with open(args.input_file, newline="") as f:
                input_lines = tuple(f)
        else:
            input_lines = tuple(sys.stdin)
    except ValueError:
        sys.exit("Text decoding error, probably binary data.")

    if output := read_csv(input_lines, any_delimiter=args.any_delimiter):
        if args.out_csv:
            write_csv(output)
        else:
            print_table(output)
    else:
        print("".join(input_lines), end="")


def read_csv(input_lines, any_delimiter=False):
    dialect = None
    delimiters = None if any_delimiter else ",\t;:"
    with suppress(csv.Error):
        dialect = csv.Sniffer().sniff("".join(input_lines), delimiters=delimiters)
    if not dialect:
        if all("\t" in line for line in input_lines):
            dialect = "excel-tab"
        elif all("," in line for line in input_lines):
            dialect = "excel"
        elif {len(line.split()) for line in input_lines if line} == {1}:
            dialect = "excel-tab"
        else:
            return None
    output = []
    with suppress(csv.Error):
        output = list(csv.reader(input_lines, dialect=dialect))
    return output


def write_csv(input_lines, pad=""):
    buffer = io.StringIO(newline="")
    writer = csv.writer(buffer)
    width = max(len(x) for x in input_lines)
    padded = (it.islice(it.chain(x, it.repeat(pad)), width) for x in input_lines)
    writer.writerows(padded)
    sys.stdout.write(buffer.getvalue())


def print_table(output, separator=" │ "):
    widths = {}
    for line in output:
        for i, field in enumerate(line):
            if len(field) > widths.get(i, 0):
                widths[i] = len(field)
    for line in output:
        print(separator.join(f"{col:{widths[i]}}" for i, col in enumerate(line)))


if __name__ == "__main__":
    sys.exit(main())