我不明白为什么这段代码不起作用！ 有人可以告诉我我做错了吗？

Question

I keep getting an error, but i dont see it.. I am new to programing and if you explane me the code, please dont assume I know too much.

#!/usr/bin/env python
# Name:
# Student number:
'''
This script crawls the IMDB top 250 movies.
'''
# Python standard library imports
import os
import sys
import csv
import codecs
import cStringIO
import errno

# Third party library imports:
import pattern
from pattern.web import URL, DOM

# --------------------------------------------------------------------------
# Constants:
TOP_250_URL = 'http://www.imdb.com/chart/top'
OUTPUT_CSV = 'top250movies.csv'
SCRIPT_DIR = os.path.split(os.path.realpath(__file__))[0]
BACKUP_DIR = os.path.join(SCRIPT_DIR, 'HTML_BACKUPS')

# --------------------------------------------------------------------------
# Unicode reading/writing functionality for the Python CSV module, taken
# from the Python.org csv module documentation (very slightly adapted).
# Source: http://docs.python.org/2/library/csv.html (retrieved 2014-03-09).

class UTF8Recoder(object):
    """
    Iterator that reads an encoded stream and reencodes the input to UTF-8
    """
    def __init__(self, f, encoding):
        self.reader = codecs.getreader(encoding)(f)

    def __iter__(self):
        return self

    def next(self):
        return self.reader.next().encode("utf-8")


class UnicodeReader(object):
    """
    A CSV reader which will iterate over lines in the CSV file "f",
    which is encoded in the given encoding.
    """

    def __init__(self, f, dialect=csv.excel, encoding="utf-8", **kwds):
        f = UTF8Recoder(f, encoding)
        self.reader = csv.reader(f, dialect=dialect, **kwds)

    def next(self):
        row = self.reader.next()
        return [unicode(s, "utf-8") for s in row]

    def __iter__(self):
        return self


class UnicodeWriter(object):
    """
    A CSV writer which will write rows to CSV file "f",
    which is encoded in the given encoding.
    """

    def __init__(self, f, dialect=csv.excel, encoding="utf-8", **kwds):
        # Redirect output to a queue
        self.queue = cStringIO.StringIO()
        self.writer = csv.writer(self.queue, dialect=dialect, **kwds)
        self.stream = f
        self.encoder = codecs.getincrementalencoder(encoding)()

    def writerow(self, row):
        self.writer.writerow([s.encode("utf-8") for s in row])
        # Fetch UTF-8 output from the queue ...
        data = self.queue.getvalue()
        data = data.decode("utf-8")
        # ... and reencode it into the target encoding
        data = self.encoder.encode(data)
        # write to the target stream
        self.stream.write(data)
        # empty queue
        self.queue.truncate(0)

    def writerows(self, rows):
        for row in rows:
            self.writerow(row)

# --------------------------------------------------------------------------
# Utility functions (no need to edit):

def create_dir(directory):
    '''
    Create directory if needed.

    Args:
        directory: string, path of directory to be made


    Note: the backup directory is used to save the HTML of the pages you
        crawl.
    '''

    try:
        os.makedirs(directory)
    except OSError as e:
        if e.errno == errno.EEXIST:
            # Backup directory already exists, no problem for this script,
            # just ignore the exception and carry on.
            pass
        else:
            # All errors other than an already exising backup directory
            # are not handled, so the exception is re-raised and the 
            # script will crash here.
            raise


def save_csv(filename, rows):
    '''
    Save CSV file with the top 250 most popular movies on IMDB.

    Args:
        filename: string filename for the CSV file
        rows: list of rows to be saved (250 movies in this exercise)
    '''
    with open(filename, 'wb') as f:
        writer = UnicodeWriter(f)  # implicitly UTF-8
        writer.writerow([
            'title', 'runtime', 'genre(s)', 'director(s)', 'writer(s)',
            'actor(s)', 'rating(s)', 'number of rating(s)'
        ])

        writer.writerows(rows)


def make_backup(filename, html):
    '''
    Save HTML to file.

    Args:
        filename: absolute path of file to save
        html: (unicode) string of the html file

    '''

    with open(filename, 'wb') as f:
        f.write(html)


def main():
    '''
    Crawl the IMDB top 250 movies, save CSV with their information.

    Note:
        This function also makes backups of the HTML files in a sub-directory
        called HTML_BACKUPS (those will be used in grading).
    '''

    # Create a directory to store copies of all the relevant HTML files (those
    # will be used in testing).
    print 'Setting up backup dir if needed ...'
    create_dir(BACKUP_DIR)

    # Make backup of the IMDB top 250 movies page
    print 'Access top 250 page, making backup ...'
    top_250_url = URL(TOP_250_URL)
    top_250_html = top_250_url.download(cached=True)
    make_backup(os.path.join(BACKUP_DIR, 'index.html'), top_250_html)

    # extract the top 250 movies
    print 'Scraping top 250 page ...'
    url_strings = scrape_top_250(top_250_url)

    # grab all relevant information from the 250 movie web pages
    rows = []
    for i, url in enumerate(url_strings):  # Enumerate, a great Python trick!
        print 'Scraping movie %d ...' % i
        # Grab web page
        movie_html = URL(url).download(cached=True)

        # Extract relevant information for each movie
        movie_dom = DOM(movie_html)
        rows.append(scrape_movie_page(movie_dom))

        # Save one of the IMDB's movie pages (for testing)
        if i == 83:
            html_file = os.path.join(BACKUP_DIR, 'movie-%03d.html' % i)
            make_backup(html_file, movie_html)

    # Save a CSV file with the relevant information for the top 250 movies.
    print 'Saving CSV ...'
    save_csv(os.path.join(SCRIPT_DIR, 'top250movies.csv'), rows)

This function below, should return the webpage links of the top 250 movies:

# --------------------------------------------------------------------------
# Functions to adapt or provide implementations for:

def scrape_top_250(url):
    '''
    Scrape the IMDB top 250 movies index page.

    Args:
        url: pattern.web.URL instance pointing to the top 250 index page

    Returns:
        A list of strings, where each string is the URL to a movie's page on
        IMDB, note that these URLS must be absolute (i.e. include the http
        part, the domain part and the path part).
    '''
    movie_urls = []

    table_rows = dom.by_id('main').by_tag('table')[1].by_tag('tr')
    for tr in table_rows[1:]:
        a = tr.by_tag('a')[0]
        movie_urls.append(clean_unicode(abs_url(a.attributes.get('href', ''), url.string)))


    # YOUR SCRAPING CODE GOES HERE, ALL YOU ARE LOOKING FOR ARE THE ABSOLUTE
    # URLS TO EACH MOVIE'S IMDB PAGE, ADD THOSE TO THE LIST movie_urls.

    # return the list of URLs of each movie's page on IMDB
    return movie_urls
#print scrape_top_250(url)

And finaly this function should return specific contents.

def scrape_movie_page(dom):
    '''
    Scrape the IMDB page for a single movie

    Args:
        dom: pattern.web.DOM instance representing the page of 1 single
            movie.

    Returns:
        A list of strings representing the following (in order): title, year,
        duration, genre(s) (semicolon separated if several), director(s) 
        (semicolon separated if several), writer(s) (semicolon separated if
        several), actor(s) (semicolon separated if several), rating, number
        of ratings.
    '''
    # YOUR SCRAPING CODE GOES HERE:


    for p in movie_urls:
        p_url = URL(p)
        p_dom = DOM(p_url.download(cached=True))

        title = clean_unicode(p_dom.by_class('header')[0].content)
        title = plaintext(strip_between('<span', '</span>', title))

        runtime = clean_unicode(p_dom.by_class('infobar')[0].by_tag('time')[0].content)
        duration = runtime

        genres = []
        for genre in p_dom.by_class('infobar')[0].by_tag('a')[:-1]:
            genres.append(clean_unicode(genre.content))

        directors = []
        writers = []
        actors = []

        text_blocks = p_dom.by_class('txt-block')[:3]
        for t in text_blocks:
            spans = t.by_tag('span')
            for s in spans:
                if s.attributes.get('itemprop') == 'director':
                    director = s.by_tag('span')[0].by_tag('a')[0].content
                    directors.append(clean_unicode(director))

                if s.attributes.get('itemprop') == 'writer':
                    p_writer = s.by_tag('span')[0].by_tag('a')[0].content
                    writers.append(clean_unicode(p_writer))

                if s.attributes.get('itemprop') == 'actors':
                    actor = s.by_tag('span')[0].by_tag('a')[0].content
                    actors.append(clean_unicode(actor))

        rating = []
        ratings_count = []

        spans = p_dom.by_class('star-box-details')[0].by_tag('span')
        for s in spans:
            if s.attributes.get('itemprop') == 'ratingValue':
                rating = clean_unicode(s.content)
            if s.attributes.get('itemprop') == 'ratingCount':
                ratings_count = clean_unicode(s.content)

        # format the strings from lists
        genres = concat_strings(genres)
        directors = concat_strings(directors)
        writers = concat_strings(writers)
        actors = concat_strings(actors)


    # Return everything of interest for this movie (all strings as specified
    # in the docstring of this function).
    return title, duration, genres, directors, writers, actors, rating, \
        n_ratings


if __name__ == '__main__':
    main()  # call into the progam

    # If you want to test the functions you wrote, you can do that here:
    # ...

Answer 1

It's just that ( in the original revision ) you forgot to indent the body of the function scrape_movie_page . The for loop is in module scope.

Answer 2

Most common reason for cause of this error due to not proper indent the body of the function , but some time code looks proper a for as indentation point of view but still it throw same error. I always saw this error comes due to mismatch in indentation .In same block if you use two type of indentation like in same block if for some line you use tab and and for some line you use spaces , code looks good as for as indentation prospective but it always through indentation error.