Gmailで検索して絞り込んだメール群のメール本文をまとめて出力する

# はじめに

GmailのLabsにあったgmailのドキュメント出力機能がなくなってしまったため、Google AppsのGmailAPIを使ってpythonで簡単に書いてみた。

## 準備

以下のドキュメント(英語)を読んで、client_secret.jsonを入手しよう。

* https://developers.google.com/gmail/api/quickstart/python

アプリケーションを定義して、ダウンロードするだけなので、1分くらいでできる。

## インストール

pipでapi clientをインストール。

```
$ pip install --upgrade google-api-python-client
```

## サンプルコード

上記のアドレスの例だと、ラベルの出力で終わってしまうので、メッセージ本文を手に入れるコードを追記、以上。

```sample.py
#!/usr/bin/env python
# -*- coding: utf-8 -*-

# from __future__ import print_function
import httplib2
import os
import base64
import logging
import traceback

from apiclient import discovery
import oauth2client
from oauth2client import client
from oauth2client import tools

try:
    import argparse
    flags = argparse.ArgumentParser(parents=[tools.argparser]).parse_args()
except ImportError:
    flags = None

SCOPES = 'https://www.googleapis.com/auth/gmail.readonly'
CLIENT_SECRET_FILE = 'client_secret.json'
APPLICATION_NAME = 'Gmail API Python Quickstart'


def get_credentials():
    """Gets valid user credentials from storage.

    If nothing has been stored, or if the stored credentials are invalid,
    the OAuth2 flow is completed to obtain the new credentials.

    Returns:
        Credentials, the obtained credential.
    """
    home_dir = os.path.expanduser('~')
    credential_dir = os.path.join(home_dir, '.credentials')
    if not os.path.exists(credential_dir):
        os.makedirs(credential_dir)
    credential_path = os.path.join(
        credential_dir,
        'gmail-python-quickstart.json'
    )

    store = oauth2client.file.Storage(credential_path)
    credentials = store.get()
    if not credentials or credentials.invalid:
        flow = client.flow_from_clientsecrets(CLIENT_SECRET_FILE, SCOPES)
        flow.user_agent = APPLICATION_NAME
        if flags:
            credentials = tools.run_flow(flow, store, flags)
        else:  # Needed only for compatibility with Python 2.6
            credentials = tools.run(flow, store)
        print('Storing credentials to ' + credential_path)
    return credentials


def extract_message(service, message):
    try:
        msg_obj = service.users().messages().get(userId='me', id=message['id'], format='raw').execute()
        return base64.urlsafe_b64decode(msg_obj['raw'].encode('ASCII'))
    except:
        logging.error(traceback.format_exc())


def extract_message_body(service, message):
    try:
        email_str = extract_message(service, message)
        subject_idx = email_str.find('Subject:')
        body_idx = email_str[subject_idx:].find(os.linesep)
        return email_str[subject_idx + body_idx:].strip()
    except:
        logging.error(traceback.format_exc())


def main():
    """Shows basic usage of the Gmail API.

    Creates a Gmail API service object and outputs a list of label names
    of the user's Gmail account.
    """
    credentials = get_credentials()
    http = credentials.authorize(httplib2.Http())
    service = discovery.build('gmail', 'v1', http=http)

    results = service.users().messages().list(userId='me', q="").execute()
    print results
    messages = results.get('messages', [])

    if not messages:
        print 'No messages found.'
    else:
        print 'messages:'
        for message in messages:
            print 'message body: ', extract_message_body(service, message)


if __name__ == '__main__':
    main()
```

検索キーワードは、list関数のqに文字列で放り込む。書式はgmailの検索と同じ。