ValueError: 转换表的长度必须为 256 个字符

Question

我有 python 烧瓶项目（程序），我将用户输入的带有大写字母和标点符号的字符串转换为没有它们的字符串。当我运行程序时，出现以下错误：

ValueError: translation table must be 256 characters long

 Traceback (most recent call last) File:

"/home/sd18656/.local/lib/python2.7/site-packages/flask/app.py", line
2463, in __call__ return self.wsgi_app(environ, start_response) File
"/home/sd18656/.local/lib/python2.7/site-packages/flask/app.py", line
2449, in wsgi_app response = self.handle_exception(e) File
"/home/sd18656/.local/lib/python2.7/site-packages/flask/app.py", line
1866, in handle_exception reraise(exc_type, exc_value, tb) File
"/home/sd18656/.local/lib/python2.7/site-packages/flask/app.py", line
2446, in wsgi_app response = self.full_dispatch_request() File
"/home/sd18656/.local/lib/python2.7/site-packages/flask/app.py", line
1951, in full_dispatch_request rv = self.handle_user_exception(e) File
"/home/sd18656/.local/lib/python2.7/site-packages/flask/app.py", line
1820, in handle_user_exception reraise(exc_type, exc_value, tb) File
"/home/sd18656/.local/lib/python2.7/site-packages/flask/app.py", line
1949, in full_dispatch_request rv = self.dispatch_request() File
"/home/sd18656/.local/lib/python2.7/site-packages/flask/app.py", line
1935, in dispatch_request return
self.view_functions[rule.endpoint](**req.view_args) File
"/home/sd18656/FlaskProject/mainapp.py", line 61, in home score,
total_processed_data = get_score(abstract) File
"/home/sd18656/FlaskProject/mainapp.py", line 32, in get_score
abstract = abstract.translate(string.punctuation).lower()

在程序中，abstract 是一个字符串类型。我遇到了这个解决方案：What does "table" in the string.translate function mean? 用于错误，但是，string.maketrans 似乎与lower() 或upper() 不匹配。我该如何解决这个问题？

导致此问题的代码sn-p如下：

r = reader(open('mycsv.csv','r'))
abstract_list = []
score_list = []
institute_list = []
row_count = 0
for row in list(r)[1:]:
    institute,score,abstract = row[0], row[1], row[2]
    if len(abstract.split()) > 0:
      institute_list.append(institute)
      score = float(score)
      score_list.append(score)
      abstract = abstract.translate(string.punctuation).lower()
      abstract_list.append(abstract)
      row_count = row_count + 1

mycsv.csv 的内容如下：

Answer 1

您需要将转换表传递给str.translate（Python 2 中的string.translate）。转换表只不过是一个dict，其中key 是搜索字符，value 是替换字符，其中key 和value 是各自字符的ord()。

例如，如果您想用空格替换所有 punctuation 字符，请执行以下操作：

from string import punctuation
transtable = string.maketrans(punctuation, ' ' * len(punctuation))

abstract = abstract.translate(transtable).lower()

这是一个概念证明：

>>> from string import punctuation
>>> transtable = string.maketrans(punctuation, ' ' * len(punctuation))
>>> type(transtable)
<class 'dict'>
>>> 'This!is#a.string,with;punctuations:'.translate(transtable).lower()
'this is a string with punctuations '
>>> 

这是maketrans 和translate 的另一个用法示例（只是为了好玩）：

>>> elite = string.maketrans('aeiou', '4310v')
>>> 'Hackers Rulez'.translate(elite)
'H4ck3rs Rvl3z'
>>>