turicas/rows

Should represent Table's fields declaration and rows instances as a class?

开放

#34 创建于 2015年8月30日

 (2 条评论) (0 个反应) (0 位负责人)Python (136 个派生)github user discovery
enhancementhelp wantedquestionrows.fields

仓库指标

星标
 (886 个星标)
PR 合并指标
 (30 天内没有已合并 PR)

描述

Currently we use two data types to represent something that could be represented in one class. The first is the fields parameter received by import_from_* (which are passed to utils.create_table), like:

UWSGI_FIELDS = OrderedDict([('pid', rows.fields.IntegerField),
                            ('ip', rows.fields.UnicodeField),
                            ('datetime', rows.fields.DatetimeField),
                            ('http_verb', rows.fields.UnicodeField),
                            ('http_path', rows.fields.UnicodeField),
                            ('generation_time', rows.fields.FloatField),
                            ('http_version', rows.fields.FloatField),
                            ('http_status', rows.fields.IntegerField)])

Second is the Table.Row (created in Table.__init__), which is a named tuple containing row data.

We could use an approach similar to ORMs and use a class to define the fields, like Django does. We could start with something like this:

class UwsgiLog(rows.Row):
    pid = rows.fields.IntegerField()
    ip = rows.fields.UnicodeField()
    datetime = rows.fields.DatetimeField()
    http_verb = rows.fields.UnicodeField()
    http_path = rows.fields.UnicodeField()
    generation_time = rows.fields.FloatField()
    http_version = rows.fields.FloatField()
    http_status = rows.fields.IntegerField()    

And the Table rows (returned when we iterate over it) will be instances of UwsgiLog.

Pros:

  • This syntax is more flexible since we can create utility methods inside the class
  • More declarative

Cons:

  • We may not have access to the field order in this case (which is very important)
  • namedtuple is probably faster than any other customized class
  • We'll need to add more complexity to the code

Note: check if we can integrate this feature with scrapy so it'll easier to parse data using rows in a scrapy project.

贡献者指南