Repository: pandas-dev/pandas
File: pandas/core/strings/accessor.py (Python)

Code before:
        1   True
        2   False
        dtype: bool
        """
        if flags is not lib.no_default:
            # pat.flags will have re.U regardless, so we need to add it here
            # before checking for a match
            flags = flags | re.U
            if is_re(pat):
                if pat.flags != flags:
                    raise ValueError(
                        "Cannot both specify 'flags' and pass a compiled regexp "
                        "object with conflicting flags"
                    )
            else:
                pat = re.compile(pat, flags=flags)
            # set flags=0 to ensure that when we call
            #  re.compile(pat, flags=flags) the constructor does not raise.
            flags = 0
        else:
            flags = 0

        if case is lib.no_default:
            if is_re(pat):
                implicit_case = not bool(pat.flags & re.IGNORECASE)
                case = True
            else:
                # Case-sensitive default
                case = True
        elif is_re(pat):
            implicit_case = not bool(pat.flags & re.IGNORECASE)
            if implicit_case != case:
                # GH#62240
                raise ValueError(
                    "Cannot both specify 'case' and pass a compiled regexp "
                    "object with conflicting case-sensitivity"
                )

        result = self._data.array._str_match(pat, case=case, flags=flags, na=na)
        return self._wrap_result(result, fill_value=na, returns_string=False)

    @forbid_nonstring_types(["bytes"])
    def fullmatch(self, pat, case: bool = True, flags: int = 0, na=lib.no_default):
        """
        Determine if each string entirely matches a regular expression.

        Checks if each string in the Series or Index fully matches the
        specified regular expression pattern. This function is useful when the
        requirement is for an entire string to conform to a pattern, such as
        validating formats like phone numbers or email addresses.


Review comment (suggestion):
Should this be:
```suggestion
        if case is lib.no_default:
            if is_re(pat):
                case = not bool(pat.flags & re.IGNORECASE)
```

Code after:
        1   True
        2   False
        dtype: bool
        """
        if flags is not lib.no_default:
            # pat.flags will have re.U regardless, so we need to add it here
            # before checking for a match
            flags = flags | re.U
            if is_re(pat):
                if pat.flags != flags:
                    raise ValueError(
                        "Cannot both specify 'flags' and pass a compiled regexp "
                        "object with conflicting flags"
                    )
            else:
                pat = re.compile(pat, flags=flags)
            # set flags=0 to ensure that when we call
            #  re.compile(pat, flags=flags) the constructor does not raise.
            flags = 0
        else:
            flags = 0

        if case is lib.no_default:
            if is_re(pat):
                case = not bool(pat.flags & re.IGNORECASE)
            else:
                # Case-sensitive default
                case = True
        elif is_re(pat):
            implicit_case = not bool(pat.flags & re.IGNORECASE)
            if implicit_case != case:
                # GH#62240
                raise ValueError(
                    "Cannot both specify 'case' and pass a compiled regexp "
                    "object with conflicting case-sensitivity"
                )

        result = self._data.array._str_match(pat, case=case, flags=flags, na=na)
        return self._wrap_result(result, fill_value=na, returns_string=False)

    @forbid_nonstring_types(["bytes"])
    def fullmatch(self, pat, case: bool = True, flags: int = 0, na=lib.no_default):
        """
        Determine if each string entirely matches a regular expression.

        Checks if each string in the Series or Index fully matches the
        specified regular expression pattern. This function is useful when the
        requirement is for an entire string to conform to a pattern, such as
        validating formats like phone numbers or email addresses.

        Parameters