Python：如何替换由某些字符括起来的字符串

Question

我想在数学表达式中替换某个变量名，而避免在函数名中替换。在

例如，以下替换n：

sin(2 pi*n d)" -> "sin(2 pi*REPL d)但不是：siREPL(2 pi*REPL d)

我的想法是检查substr是否被特殊字符（' '、'('、'*'等）括在一起，但我没有将其放入regex或python代码中。在

有什么想法吗？在

Answer 1

使用词边界（\b）

>>> import re
>>> re.sub(r'\bn\b', 'REPL', 'sin(2 pi*n d)')
'sin(2 pi*REPL d)'

根据^{} module documentation：

\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, ...