python and scrapy THE encoding issue

问题:

I simple can't figure out! :( I am scrapping data from an utf-8 encoded site, well that is at least what it says:

Content-Type: text/html;charset=utf-8

I am getting a list of regular unicode strings with XPath selector extract() call:

item['city']= element.select('//div[@id="bubble_2"]/div/text()').extract()

This is the list:

[u'Westbahnhofstr.\xa010', u'72070\xa0T\xfcbingen']

Now I join the list into one unicode string:

item['city']= "".join(element.select('//div[@id="bubble_2"]/div/text()').extract())

So far so good:

u'Beim Nonnenhaus\xa0672070\xa0T\xfcbingen'

The problem appears while I try to output this unicode string either to screen (print) or to a file (write). whatever I try it returns an error (http://pastebin.com/51DkX2R2):

exceptions.UnicodeEncodeError: 'ascii' codec can't encode character u'\xa0' in   position 11: ordinal not in range(128)

I have encoded unicode to byte string before output of course:

item['city'].encode('utf-8')

This is my pipeline.py and how I use to open and write to my cvs:

import csv
import items
import urlparse
import codecs

class DepostPipeline(object):
    def __init__(self):
        self.modelsCsv = csv.writer(codecs.open('Dees.csv', mode='w',encoding='utf-8'))
        self.modelsCsv.writerow(['city'])

def process_item(self, item, spider):
    if isinstance(item, items.DetailsItem): 
        item['city'] = item['city'].encode('utf-8')

        self.modelsCsv.writerow([item['city']]) 
        return item

The most weird thing is that my system (python on windows) handles unicode strings perfectly:

C:\Console2>python
Python 2.7.6 (default, Nov 10 2013, 19:24:18) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> s=u'Beim Nonnenhaus\xa0672070\xa0T\xfcbingen'
>>> print s
Beim Nonnenhaus 672070 Tübingen

I have been reading about utf-8, unicode, encoding and decoding a lot over the last 10 days but it seems that I still miss something here?! I appreciate any help or advice.

回答1:

You are ignoring the result of the .encode() call:

item['city'].encode('utf-8')

Strings are immutable, and are not encoded in-place. Even better, the type of the returned object is different. You'll need to assign the return value back:

item['city'] = item['city'].encode('utf-8')

However, you should not use codecs.open() for the CSV file. The csv module will always write bytestrings, not Unicode.

By using a codecs.open() file object, an implicit decode takes place to get back to Unicode, and it is that that fails for you; it is why you get a UnicodeDecodeError exception, not an encode error:

  File "C:\Python27\lib\codecs.py", line 351, in write
    data, consumed = self.encode(object, self.errors)
exceptions.UnicodeDecodeError: 'ascii' codec can't decode byte 0xc2 in position 11: ordinal not in range(128)

Use a regular open() call instead:

self.modelsCsv = csv.writer(open('Dees.csv', mode='wb'))

Note the 'wb'; the csv module handles line endings itself.

回答2:

You can use "ignore" parameter:

item['city'].encode('utf-8', 'ignore')

https://docs.python.org/2/howto/unicode.html#the-unicode-type