Python - Exception Handling: What to Do When Things Go Wrong(Creating Custom Exceptions)

Head First Python

開発環境

• macOS Sierra - Apple (OS)
• Emacs (Text Editor)
• Python 3.6 (プログラミング言語)

Head First Python (Paul Barry (著)、O'Reilly Media)のChapter 11.(Exception Handling: What to Do When Things Go Wrong) の SHARPEN YOUR PENCIL(No. 8290) を取り組んでみる。

SHARPEN YOUR PENCIL(No. 8290)

コード(Emacs)

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import sqlite3


class CustomException(Exception):
    pass


class UseDatabase:

    def __init__(self, dbconfig: dict) -> None:
        self.dbconfig = dbconfig

    def __enter__(self) -> 'cursor':
        try:
            self.conn = sqlite3.connect(self.dbconfig['database'] + '.sql')
            self.cursor = self.conn.cursor()
            return self.cursor
        except Exception as err:
            raise CustomException('custom exception')

    def __exit__(self, exc_type, exc_value, exc_trace) -> None:

        self.conn.commit()
        self.cursor.close()
        self.conn.close()

if __name__ == '__main__':
    dbconfig = {'host': '127.0.0.1',
                'user': 'vsearch',
                'password': 'vsearchpasswd',
                'database': 'vsearchlogDB'}
    with UseDatabase() as cursor:
        _SQL = '''select * from log'''
        cursor.execute(_SQL)
        for row in cursor.fetchall():
            print(row)

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

# cursor.execute('''create table log (
# id int auto_increment primary key,
# ts timestamp default current_timestamp,
# phrase varchar(128) not null,
# letters varchar(32) not null,
# ip varchar(16) not null,
# browser_string varchar(256) not null,
# results varchar(64) not null )''')

from flask import Flask, render_template, request, escape
from DBcm import UseDatabase, CustomException

import sqlite3

import vsearch

app = Flask(__name__)

app.config['dbconfig'] = {'host': '127.0.0.1',
                          'user': 'vsearch',
                          'password': 'vsearchpasswd',
                          'database': 'vsearchlogDB'}


def log_request(req: 'flask_request', res: str) -> None:
    # with UseDatabase(app.config['dbconfig']) as cursor:
    with UseDatabase('') as cursor:
        _SQL = '''insert into log
                  (phrase, letters, ip, browser_string, results)
                  values
                  (?, ?, ?, ?, ?)'''
        cursor.execute(_SQL, (req.form['phrase'],
                              req.form['letters'],
                              req.remote_addr,
                              req.user_agent.browser,
                              res))


@app.route('/')
@app.route('/entry')
def entr_page() -> 'html':
    return render_template('entry.html',
                           the_title='Welcome to search4letters on the web!')


@app.route('/search4', methods=['POST'])
def do_search() -> 'html':
    phrase = request.form['phrase']
    letters = request.form['letters']
    title = 'Here are your result:'
    results = str(vsearch.search4letters(phrase, letters))
    try:
        log_request(request, results)
    except CustomException as err:
        print(err)
    except Exception as err:
        print(err)
    return render_template('results.html',
                           the_title=title,
                           the_phrase=phrase,
                           the_letters=letters,
                           the_results=results)


@app.route('/viewlog')
def view_the_log() -> 'html':
    with UseDatabase(app.config['dbconfig']) as cursor:
        _SQL = 'select phrase, letters, ip, browser_string, results from log'
        cursor.execute(_SQL)
        contents = cursor.fetchall()
    titles = ('Phrase', 'Letters', 'Remote_addr', 'User_agent', 'Results')
    return render_template('viewlog.html',
                           the_title='View Log',
                           the_row_titles=titles,
                           the_data=contents,)

if __name__ == '__main__':
    app.run(debug=True)

入出力結果(Terminal, IPython)

$ ./vsearch4log.py
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 873-014-066
127.0.0.1 - - [14/Apr/2017 14:08:04] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [14/Apr/2017 14:08:04] "GET /static/hf.css HTTP/1.1" 304 -
custom exception
127.0.0.1 - - [14/Apr/2017 14:08:10] "POST /search4 HTTP/1.1" 200 -
  C-c C-c
$