在re.search中使用“|”的TypeError（“RE”|“RE”|“RE”，字符串）

Question

According to the docs, "|" can be used to create a regular expression that matches either of the patterns separated by "|".

I am trying to use the following to see if moves contains a string that matches one of "UP""DOWN""LEFT""RIGHT":

moves = input("UP 9")
m = re.search("UP"|"DOWN"|"LEFT"|"RIGHT", moves)

But I keep getting the "TypeError: unsupported operand type(s) for |: 'str' and 'str'" . How to fix it?

I tried looking online but there are few samples that show the use of "|" in re. Is it not commonly used for some reason?

Answer 1

This is, unfortunately a typo, but the answer goes a little deeper than that.

| is the bitwise OR operator. It is defined for integers only, not strings. On the other hand, the "|" character (note the quotes) is the regex OR pipe, and is used to specify a conjunction on patterns.

In summary, the | needs to be inside the pattern string, not outside.

m = re.search("UP|DOWN|LEFT|RIGHT", moves)

For more information on the various constructs available in regular expression mini-language, see the official Regular Expression HOWTO . The subsection on Regex Metacharacters , in particular (which explains the use of the OR pipe amongst others) should be helpful.