scrapy类Field是否具有存储字符串的最大大小？

Question

我正在尝试将字符串存储到scrapy Item类中，但是当字符串超过67个字符时，它会自动截断为两个字符串。

import scrapy
from scrapy import Item, Field


class InfoItem(Item):
    info = Field()

class TopicItem(Item):
    topic = Field()
    categories = Field()

class CategoryItem(Item):
    category = Field()
    fields = Field()

class FieldItem(Item):
    field = Field()
    value = Field()

class QuotesSpider(scrapy.Spider):
    name = "categories"

    def start_requests(self):
        urls = ['http://www.eustat.euskadi.eus/t35-t64cont/eu/t64amVisorWar/t64aIndicadores.jsp?language=0']
        for url in urls:
            yield scrapy.Request(url=url, callback=self.parse)

    def parse(self, response):

        info_item = InfoItem()
        info_item['info'] = []

        for i, eje in enumerate(response.css('h1.eje')):
            text = response.css('h1.eje::text')[i].extract()

            topic_item = TopicItem()
            topic_item['topic'] = text
            topic_item['categories'] = []
            info_item['info'].append(topic_item)

            siblings = eje.xpath('following-sibling::div')
            print(siblings)
            div_sibling = siblings[0]
            print(div_sibling)
            for j, h2 in enumerate(div_sibling.css('h2')):
                text = div_sibling.css('h2::text')[j].extract()

                category_item = CategoryItem()
                category_item['category'] = text
                category_item['fields'] = []

                div_siblings_h2 = h2.xpath('following-sibling::div')
                div_sibling_h2 = div_siblings_h2[0]

                for h3 in div_sibling_h2.css('h3'):
                    the_input = h3.xpath('input//following-sibling::text()')[0].extract()[:-1]
                    input_value = h3.xpath('input/@value').extract().pop()

                    field_item = FieldItem()
                    field_item['field'] = the_input[:66] (*)
                    field_item['value'] = input_value
                    category_item['fields'].append(field_item)

                topic_item['categories'].append(category_item)

        print(info_item)

（*）如果我没有截断这个字符串，最后一条打印指令会显示'the_input'变量的最长值是如何分成两个字符串的。例如：

'fields': [
    {'field': 'Superficie ocupada por parques, jardines y zonas verdes urbanas (%', 
     'value': '142'},

不截断：

'fields': [
    {'field': 'Superficie ocupada por parques, jardines y zonas verdes urbanas ''(%/suelo urbano)',
    'value': '142'},

环境：

OS: Ubuntu 16.04.2
python: 3.5.2
Scrapy == 1.3.3