はじめてのリスト内包表記

課題

# この入力に対して
service = {'Yahoo!': 'www.yahoo.co.jp', 'Google': "www.google.com", 'MSN': 'www.msn.com', 'wiki': 'ja.wikipedia.org'}

# この結果を得たいとする
# www_urls = 'www.yahoo.co.jp,www.google.com,www.msn.com,'
# other_urls  = 'ja.wikipedia.org'

ベタ書き

    www_urls = ''
    other_urls = ''
    for service_name in service:
        url = service[service_name]
        if 'www' in url:
            www_urls = www_urls + url + ','
        else:
            other_urls = other_urls + url + ','
    www_urls = www_urls[:-1]
    other_urls = other_urls[:-1]

    print(www_urls)
    print(other_urls)

カッコワルイ

リスト内法表記

    www_urls_list = [service[service_name] for service_name in service if 'www' in service[service_name]]
    other_urls_list = [service[service_name] for service_name in service if 'www' not in service[service_name]]
    www_urls = ','.join(www_urls_list)
    other_urls = ','.join(other_urls_list)

    print(www_urls)
    print(other_urls)

さらにまとめて

    www_urls = ','.join([service[service_name] for service_name in service if 'www' in service[service_name]])
    other_urls = ','.join([service[service_name] for service_name in service if 'www' not in service[service_name]])

    print(www_urls)
    print(other_urls)