python re.sub 组 : number after\number

Question

如何将 foobar 替换为 foo123bar？

这不起作用:

>>> re.sub(r'(foo)', r'\1123', 'foobar')
'J3bar'

这行得通:

>>> re.sub(r'(foo)', r'\1hi', 'foobar')
'foohibar'

我认为当有 \number 之类的内容时，这是一个常见问题。谁能给我一个关于如何处理这个问题的提示？

Answer 1

答案是:

re.sub(r'(foo)', r'\g<1>123', 'foobar')

文档的相关摘录:

In addition to character escapes and backreferences as described above, \g will use the substring matched by the group named name, as defined by the (?P...) syntax. \g uses the corresponding group number; \g<2> is therefore equivalent to \2, but isn’t ambiguous in a replacement such as \g<2>0. \20 would be interpreted as a reference to group 20, not a reference to group 2 followed by the literal character '0'. The backreference \g<0> substitutes in the entire substring matched by the RE.