Python regular expression returns the first match to the character and the robustness of the query

Re.findall (pattern,string) searches for all matching characters, returns a list, gets the first match to be accessed Re.findall (pattern,string) [0], but returns an empty list if the FindAll does not match successfully. When you use the list subscript to access the element, you will be quoted Indexerror:list index out of range.

Such as:

>>>re.findall ('abc','abd') []>> >re.findall ('abc','abd' ) <input> "  in <module>indexerror:list index out of range

We can add a "|$" behind the pattern to generate a default ' element:

>>>re.findall ('abc|$','abd') [0] >>>re.findall ('abc|$','abcdef ' # Note that the previous ' element ' will be appended, regardless of whether it matches or not ['abc']

The same applies to Re.search

>>> re.search ('\d+|$'aa33bbb44'). Group ()  're.search'>>> ('\d+|$' ) aazzzbbb ' ). Group ()'

If you don't add |$:

>>>re.search ('\d+'aazzzbbb'" ) <input> "  in <module>'nonetype'group '

Reference: Https://stackoverflow.com/questions/38579725/return-string-with-first-match-regex

Python regular expression returns the first match to the character and the robustness of the query