我正在构建一些模板到我的应用程序中，它采用这样的字符串：
templateString = r'{title} {- author} ({timestamp})'
并替换模板{}中的相应字符串（如果存在）：
# 10 things on my todo list - Brandon (2018-01-01 00:00:01)
我想在模板字符串中允许自定义字符，以便用户可以连字符或括号或其他内容，但仅当存在这些属性时，例如如果作者是空的，你不想看到：
# 10 things on my todo list - (2018-01-01 00:00:01)
你想看到：
# 10 things on my todo list (2018-01-01 00:00:01)
为此，我尝试使用捕获组来抓取{，识别字和}之间存在的任何文字：
titleExp = re.compile(r'\{([^\{]*)title([^\}]*)\}', re.I)
authorExp = re.compile(r'\{([^\{]*)author([^\}]*)\}', re.I)
timestampExp = re.compile(r'\{([^\{]*)timestamp([^\}]*)\}', re.I)
超级奇怪的是，当我尝试使用原始字符串替换r'\1{}\2'）时，而不是我的待办事项列表中的＆＃34; 10件事，我得到＆＃34; 34;我的待办事项清单上的东西＆＃34;：
templateString = r'{title} {- author} ({timestamp})'
self.title = "10 things on my todo list"
renamed = re.sub(titleExp, (r'\1{}\2' if self.title else '').format(self.title or ''), renamed)
# H things on my todo list ...
我当然尝试没有原始字符串：
templateString = r'{title} {- author} ({timestamp})'
self.title = "10 things on my todo list"
renamed = re.sub(titleExp, ('\\1{}\\2' if self.title else '').format(self.title or ''), renamed)
# 10 things on my todo list ...
但同样的事情发生了。
发生了什么？为什么原始字符串会搞定？我可以说它特意与数字有关，而且捕获组可能没有正确行事。
结束重现：
templateString = r'{title} {- author} ({timestamp})'
titleExp = re.compile(r'\{([^\{]*)title([^\}]*)\}', re.I)
authorExp = re.compile(r'\{([^\{]*)author([^\}]*)\}', re.I)
timestampExp = re.compile(r'\{([^\{]*)timestamp([^\}]*)\}', re.I)
title = "10 things on my todo list"
author = "Brandon"
timestamp = "2018-01-01 00:00:01"
templateString = re.sub(titleExp, r'\1{}\2'.format(title), templateString)
templateString = re.sub(authorExp, r'\1{}\2'.format(author), templateString)
templateString = re.sub(timestampExp, r'\1{}\2'.format(timestamp), templateString)
print(templateString)
# output:
# H things on my todo list - Brandon (P18-01-01 00:00:01)
# ^ ?? ^ ??
# expected:
# 10 things on my todo list - Brandon (2018-01-01 00:00:01)
更多研究：
它似乎与替换字符串的第一个字符有关：
title = " 10 things on my todo list"
#. ^ space
author = "Brandon"
timestamp = " 2018-01-01 00:00:01"
#. ^ space
修复它......有点......
答案 0 :(得分：0)
您可以将firebase: "Help"
the the resulting favourites object should be
favorites: { food: "Pizza", color: "Blue", subject: "recess", firebase: "Help" },
置于"-"占位符之外，然后使用{author}：
re.sub输出：
import re
templateString = r'{title} - {author} ({timestamp})'
title = "10 things on my todo list"
author = "Brandon"
timestamp = "2018-01-01 00:00:01"
new_data = re.sub('-\s(?=\{author)', '', templateString).format(title=title, author=author, timestamp = timestamp) if not author else templateString.format(title=title, author=author, timestamp = timestamp)
print(new_data)
当10 things on my todo list - Brandon (2018-01-01 00:00:01)
为空时：
author输出：
title = "10 things on my todo list"
author = ""
timestamp = "2018-01-01 00:00:01"
new_data = re.sub('-\s(?=\{author)', '', templateString).format(title=title, author=author, timestamp = timestamp) if not author else templateString.format(title=title, author=author, timestamp = timestamp)
print(new_data)
答案 1 :(得分：0)
对于它的价值，如果我在不使用内联捕获组的情况下突破表达式，它的行为正确。我现在可以用这个作为解决方法，但我肯定会喜欢解释为什么......
templateString = r'{title} {- author} ({timestamp})'
titleExp = re.compile(r'\{([^\{]*)title([^\}]*)\}', re.I)
authorExp = re.compile(r'\{([^\{]*)author([^\}]*)\}', re.I)
timestampExp = re.compile(r'\{([^\{]*)timestamp([^\}]*)\}', re.I)
title = "10 things on my todo list"
author = "Brandon"
timestamp = "2018-01-01 00:00:01"
match = re.search(titleExp, templateString)
title = '{}{}{}'.format(match.groups()[0], title, match.groups()[1])
templateString = re.sub(titleExp, title, templateString)
match = re.search(authorExp, templateString)
author = '{}{}{}'.format(match.groups()[0], author, match.groups()[1])
templateString = re.sub(authorExp, author, templateString)
match = re.search(timestampExp, templateString)
timestamp = '{}{}{}'.format(match.groups()[0], timestamp, match.groups()[1])
templateString = re.sub(timestampExp, timestamp, templateString)
print templateString
# output:
# 10 things on my todo list - Brandon (2018-01-01 00:00:01)