Python使用re.sub和dict替换配额和撇号

Question

I'm trying to replace ' and " in a sting. Here is the dict:

char_replace_list = {
    '"': '"',
    "'": ''',
    '&': '&',
    '<': '&lt',
    '>': '&gt',
}

This is what I did:

s = '\' " & < >'
pattern = re.compile(r'\b(' + '|'.join(self.char_replace_list.keys()) + r')\b')
pattern.sub(lambda x: char_replace_list[x.group()], s)

The result is:

' " & < >

Where did I do wrong?

Answer 1

Interestingly I get a different result, with no substitutions at all on my machine.

Your issue is that the edges of those punctuation characters are not considered word boundaries (in a platform-dependent way!?):

\\b

Matches the empty string, but only at the beginning or end of a word. A word is defined as a sequence of alphanumeric or underscore characters , so the end of a word is indicated by whitespace or a non-alphanumeric, non-underscore character. Note that formally, \\b is defined as the boundary between a \\w and a \\W character (or vice versa), or between \\w and the beginning/end of the string, so the precise set of characters deemed to be alphanumeric depends on the values of the UNICODE and LOCALE flags . For example, r'\\bfoo\\b' matches 'foo' , 'foo.' , '(foo)' , 'bar foo baz' but not 'foobar' or 'foo3' . Inside a character range, \\b represents the backspace character, for compatibility with Python's string literals.

Instead of \\b...\\b you could use (?<= |^)...(?= |$)

Answer 2

I this case you can use translate method:

char_replace_list = {
    '"': '"',
    "'": ''',
    '&': '&',
    '<': '&lt',
    '>': '&gt',
}
s = '\' " & < >'
# table translate from a mapping
t = "".maketrans(char_replace_list)
print(s.translate(t))
# &apos; &quot; &amp; &lt &gt