Write a regex for a pattern?

a + (ab or cd ) + g is my expression. How can I write a regex 开发者_如何学Cin Python to match these?

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To search this regex in a string, say

re.search("a\\+((ab)|(cd))\\+g", your_string)

To extract matches, use re.findall etc. No need to copy&paste the docs here. :)

EDIT: Updated after OP changed the regex.

If you want it to match whitespace in between, things get pretty ugly ...

re.search("a\W*\\+\W*((ab)|(cd))\W*\\+\W*g", your_string)