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

我一直收到错误，但是我看不到..我是编程新手，如果您对我的代码进行平面编程，请不要以为我知道太多。

#!/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)

以下功能可返回前250部电影的网页链接：

# --------------------------------------------------------------------------
# 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)

最后，此函数应返回特定内容。

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

只是（ 在原始版本中 ）您忘了缩进函数scrape_movie_page的主体。 for循环在模块范围内。

Answer 2

由于不正确地缩进函数的主体而导致此错误的最常见原因，但是从缩进的角度来看，某些时间代码看起来是正确的，但仍然会引发相同的错误。 我总是看到此错误是由于缩进不匹配引起的。在同一块中，如果您使用两种类型的缩进，例如在同一块中，如果对于某些行使用tab并对于某些行使用空格 ，则代码看起来像缩进一样但是它总是通过缩进错误。