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41 lines
1.2 KiB
XML
41 lines
1.2 KiB
XML
<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p>
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The meaning of the <code>\b</code> escape sequence inside a regular expression depends on its
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syntactic context: inside a character class, it matches the backspace character; outside of a
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character class, it matches a word boundary. This context dependency makes regular expressions
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hard to read, so the <code>\b</code> escape sequence should not be used inside character classes.
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</p>
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</overview>
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<recommendation>
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<p>
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Replace <code>\b</code> in character classes with the semantically identical escape sequence <code>\x08</code>.
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</p>
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</recommendation>
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<example>
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<p>
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In the following example, the regular expression contains two uses of <code>\b</code>: in the
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first case, it matches a word boundary, in the second case it matches a backspace character.
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</p>
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<sample src="BackspaceEscape.py" />
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<p>
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You can make the regular expression easier for other developers to interpret, by rewriting it as <code>r"\b[\t\x08]"</code>.
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</p>
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</example>
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<references>
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<li>Python Standard Library: <a href="https://docs.python.org/library/re.html">Regular expression operations</a>.</li>
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</references>
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</qhelp>
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