My Oracle Shell

main.py

# Alternative shell for Oracle database.
# Alpha version, do not use for production purposes.
#
# Author: 2016 Dmitry Shachnev <[email protected]>

import readline
import shutil
import sys
import cx_Oracle

def resize(string, length, fill_character=' '):
    if length < len(string):
        return string[:length]
    return string + fill_character * (length - len(string))

def format_headers(headers, lines):
    columns = shutil.get_terminal_size().columns
    header_names = list(zip(*headers))[0]
    lines_stringified = [list(map(str, line)) for line in lines]
    max_lengths = [max(map(len, column)) for column in zip(*[header_names] + lines_stringified)]
    max_possible_sum = columns - 3 * (len(max_lengths) - 1)
    lengths_sum = sum(max_lengths)
    if lengths_sum > max_possible_sum:
        max_lengths = [length * max_possible_sum // lengths_sum for length in max_lengths]
        while sum(max_lengths) < max_possible_sum:
            max_diff = 0
            index = None
            for i, column in enumerate(zip(*lines_stringified)):
                diff = max(map(len, column)) - max_lengths[i]
                if diff > max_diff:
                    max_diff, index = diff, i
            if index is not None:
                max_lengths[index] += 1
    new_headers = (resize(*pair) for pair in zip(header_names, max_lengths))
    print(' | '.join(new_headers))
    print('-+-'.join('-' * length for length in max_lengths))
    for line in lines_stringified:
        new_items = (resize(*pair) for pair in zip(line, max_lengths))
        print(' | '.join(new_items))

def execute_query(query, query_args, cursor):
    cursor.execute(query, query_args)
    format_headers(cursor.description, cursor)

def process_query(line, cursor):
    query = line
    query_args = {}
    if line.lower().startswith('desc '):
        query = "select COLUMN_NAME, DATA_TYPE, NULLABLE from COLS where TABLE_NAME = :table_name"
        query_args["table_name"] = line[5:].upper()
    try:
        execute_query(query, query_args, cursor)
    except cx_Oracle.DatabaseError as exc:
        error, = exc.args
        print(error.message, file=sys.stderr)

def main(argv):
    if len(argv) < 2:
        sys.exit("usage: %s <logon string>" % sys.argv[0])
    try:
        connection = cx_Oracle.Connection(argv[1])
    except cx_Oracle.DatabaseError as exc:
        error, = exc.args
        sys.exit(error.message)
    cursor = connection.cursor()
    while True:
        try:
            line = input('SQL> ')
        except EOFError:
            print()
            break
        process_query(line, cursor)


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