带有标志的Python re.sub不能替换所有出现的

Question

Python文档说：

re.MULTILINE: When specified, the pattern character '^' matches at the beginning of the string and at the beginning of each line (immediately following each newline)... By default, '^' matches only at the beginning of the string...

所以当我得到以下意想不到的结果时发生了什么？

>>> import re
>>> s = """// The quick brown fox.
... // Jumped over the lazy dog."""
>>> re.sub('^//', '', s, re.MULTILINE)
' The quick brown fox.\n// Jumped over the lazy dog.'

Answer 1

^{}的完整定义是：

re.sub(pattern, repl, string[, count, flags])

这意味着，如果告诉Python参数是什么，那么就可以传递flags，而不传递count：

re.sub('^//', '', s, flags=re.MULTILINE)

或者，更简洁地说：

re.sub('^//', '', s, flags=re.M)