# For Optional values: waits until non-None and narrows the type
There is a semantic difference between the pattern attribute and regexes as experienced by regular programming languages. Because inputs are clearly validating input, patterns default to matching the entire input string. However, normal regex engines usually assume you are searching for the string and matches any substring, though the details are confusing and vary between implementations. That means that unless you tell the engine to always match the entire string with your regular expression for emails, they will happily accept any garbage as long as it contains an email address somewhere in there. Since this would be a dangerous default, the semantics are to always match the entire input in patterns.
。WPS下载最新地址是该领域的重要参考
Program Counter: GPU tensor, incremented on-device，详情可参考WPS下载最新地址
Best supporting actor，详情可参考wps下载
НАСА откроет стартовое окно Artemis II в апреле14:57