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我正在编写一个脚本来解析一封电子邮件，但SyntaxError在以下部分的 for 循环中有一些：

def main():
     writer = csv.DictWriter(open('features.csv', 'w'), list(EXTRACTS.keys()))
     for mail in os.listdir(MAILDIR):
         writer.writerow({
                key: value(email.message_from_file(open(os.path.join(MAILDIR, mail), 'r')))
            for key, value in EXTRACTS.items()
             })

请帮我解决这个问题！

编辑：

文件“/IS/extraction.py”，第 52 行

for key, value in EXTRACTS.items()
  ^ SyntaxError: invalid syntax
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1 回答 1

2

您在不支持字典推导的旧 Python 版本上运行它。该{key: value for ... in ...}语法仅在 Python 2.7 和更新版本中可用：

Python 2.6.8 (unknown, May 22 2013, 11:58:55) 
[GCC 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.11.00)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> def main():
...      writer = csv.DictWriter(open('features.csv', 'w'), list(EXTRACTS.keys()))
...      for mail in os.listdir(MAILDIR):
...          writer.writerow({
...                 key: value(email.message_from_file(open(os.path.join(MAILDIR, mail), 'r')))
...             for key, value in EXTRACTS.items()
  File "<stdin>", line 6
    for key, value in EXTRACTS.items()
      ^
SyntaxError: invalid syntax

用字典构造函数和生成器表达式替换该行：

writer.writerow(dict(
    (key, value(email.message_from_file(open(os.path.join(MAILDIR, mail), 'r'))))
    for key, value in EXTRACTS.items()
))

但是，您确实希望避免阅读每个关键项对的电子邮件EXTRACTS；每个外循环读取一次：

def main():
    writer = csv.DictWriter(open('features.csv', 'w'), list(EXTRACTS.keys()))
    for mail in os.listdir(MAILDIR):
        mail = email.message_from_file(open(os.path.join(MAILDIR, mail), 'r'))
        writer.writerow(dict((key, value(mail)) for key, value in EXTRACTS.items()))
于 2013-10-18T19:05:39.737 回答