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从googleappengine中的文件生成json的正确方法是什么?

file-io google-app-engine python

erotsppa · 技术社区 · 16 年前

我对python和gae很陌生,有人能为完成以下简单任务提供一些帮助/示例代码吗?我设法读取了一个简单的文件并将其作为网页输出,但我需要一些稍微复杂一些的逻辑。以下是伪代码:

  open file;
  for each line in file {
    store first line as album title;
    for each song read {
      store first line as song title;
      store second line as song URL;
    }
  }
  Output the read in data as a json;

文件格式如下

专辑标题1
宋题
歌曲1网址
歌曲2标题
Song2网址

专辑TILL2
宋题
歌曲1网址
歌曲2标题
歌曲2网址
…

2 回复 | 直到 16 年前

Kenan Banks 16 年前

下面是一个基于生成器的解决方案,它有一些好的特性:

允许文本文件中相册之间有多个空行
允许文本文件中的前导/尾随空行
一次只使用一张专辑的内存
演示了许多可以用python进行的neato操作:)

相册

Album title1
song1 title
song1 url
song2 title
song2 url

Album title2
song1 title
song1 url
song2 title
song2 url

代码

from django.utils import simplejson

def gen_groups(lines):
   """ Returns contiguous groups of lines in a file """

   group = []

   for line in lines:
      line = line.strip()
      if not line and group:
         yield group
         group = []
      elif line:
         group.append(line)


def gen_albums(groups):
   """ Given groups of lines in an album file, returns albums  """

   for group in groups:
      title    = group.pop(0)
      songinfo = zip(*[iter(group)]*2)
      songs    = [dict(title=title,url=url) for title,url in songinfo]
      album    = dict(title=title, songs=songs)

      yield album


input = open('albums.txt')
groups = gen_groups(input)
albums = gen_albums(groups)

print simplejson.dumps(list(albums))

产量

[{"songs": [{"url": "song1 url", "title": "song1 title"}, {"url": "song2 url", "title": "song2 title"}], "title": "song2
title"},
{"songs": [{"url": "song1 url", "title": "song1 title"}, {"url": "song2 url", "title": "song2 title"}], "title": "song2
title"}]

然后可以在javascript中访问相册信息,如下所示:

var url = albums[1].songs[0].url;

最后,这是一个关于 tricky zip line .

Alex Martelli 16 年前

from django.utils import simplejson

def albums(f):
  "" yields lists of strings which are the
     stripped lines for an album (blocks of
     nonblank lines separated by blocks of
     blank ones.
  """
  while True:
    # skip leading blank lines if any
    for line in f:
      if not line: return
      line = line.strip()
      if line: break
    result = [line]
    # read up to next blank line or EOF
    for line in f:
      if not line:
        yield result
        return
      line = line.strip()
      if not line: break
      result.append(line)
    yield result

def songs(album):
  """ yields lists of 2 lines, one list per song.
  """
  for i in xrange(1, len(album), 2):
    yield (album[i:i+2] + ['??'])[:2]

result = dict()
f = open('thefile.txt')
for albumlines in albums(f):
  current = result[albumlines[0]] = []
  for songlines in songs(albumlines):
    current.append( {
      'songtitle': songlines[0],
      'songurl': songlines[1]
    } )

response.out.write(simplejson.dumps(result))