UnboundLocalError: local variable 'items' referenced before assignment [duplicate]

问题

Possible Duplicate:
convert list to string to insert into my sql in one row in python scrapy

I am trying to write the data extracted from HTML pages directly to a MySQL database. But the code, which used to work, no longer does. Can someone please help me out?

def parse(self, response):
    hxs = HtmlXPathSelector(response)
    sites = hxs.select('//ul/li')
    con = MySQLdb.connect(
        host="localhost",
        user="dreamriks",
        passwd="dreamriks",
        db="scraped_data"
    )
    cur = con.cursor()
    for site in sites:
        items = [site.select('//h2').extract()]
        item = [site.select('//h3').extract()]
        meta = [site.select('//meta').extract()]
    for index in range (len( items)):              #<-- exception raises here
        str = items[index]
        cur.execute("""Insert into h2_meta(h2) Values(%s)""",(str))
    con.commit()
    con.close()

The code above gives the following error:

exceptions.UnboundLocalError: local variable 'items' referenced before assignment

回答1:

Your indention is broken. Indent the block

for index in range (len( items)):
    str = items[index]
    cur.execute("""Insert into h2_meta(h2) Values(%s)""",(str))

four more spaces.

回答2:

It looks like you have an indenting problem. The for index in range(len(items)) is part of the for site in sites loop, right?

    for site in sites:
        items = [site.select('//h2').extract()]
        item = [site.select('//h3').extract()]
        meta = [site.select('//meta').extract()]
        for index in range (len( items)):             # <-- make sure this has same
             str = items[index]                       # level of indenting as previous lines
             cur.execute("""Insert into h2_meta(h2) Values(%s)""",(str))

回答3:

If for site in sites: doesn't iterate because sites is empty, then items never gets initialised.

When you reference it in for index in range (len( items)): the code is assuming that items has been intialised.

来源：https://stackoverflow.com/questions/9079560/unboundlocalerror-local-variable-items-referenced-before-assignment

标签

python

variable-assignment