我把它的全部代码贴出来，这是 configparser 模块里用于读取 Ini 文件的 get 方法。

```python
def get(self, section, option, *, raw=False, vars=None, fallback=_UNSET):
"""Get an option value for a given section.

If `vars' is provided, it must be a dictionary. The option is looked up
in `vars' (if provided), `section', and in `DEFAULTSECT' in that order.
If the key is not found and `fallback' is provided, it is used as
a fallback value. `None' can be provided as a `fallback' value.

If interpolation is enabled and the optional argument `raw' is False,
all interpolations are expanded in the return values.

Arguments `raw', `vars', and `fallback' are keyword only.

The section DEFAULT is special.
"""
try:
d = self._unify_values(section, vars)
except NoSectionError:
if fallback is _UNSET:
raise
else:
return fallback
option = self.optionxform(option)
try:
value = d[option]
except KeyError:
if fallback is _UNSET:
raise NoOptionError(option, section)
else:
return fallback

if raw or value is None:
return value
else:
return self._interpolation.before_get(self, section, option, value,
d)
```