英文:
How to understand a line of dead code in a python function?
问题
以下是您要翻译的部分：
def t_newline(t):
r'\n+'
t.lexer.lineno += t.value.count("\n")
英文:
The following code comes from Ply, python’s lexer and parser. I understand the first line is a raw string but I also feel that the first line of the code looks like dead code and will be discarded in execution. How could I understand that line of code?
def t_newline(t):
r'\n+'
t.lexer.lineno += t.value.count("\n")
答案1
得分: 4
It's actually a docstring, so that's not "dead code".
```python
def t_newline(t):
r'\n'
t.lexer.lineno += 1
t_newline.__doc__
'\n'
ply.lex consumes them.
<details>
<summary>英文:</summary>
It's actually a docstring, so that's not "dead code".
>>> def t_newline(t):
... r'\n'
... t.lexer.lineno += 1
...
>>> t_newline.doc
'\n'
[`ply.lex`](https://github.com/dabeaz/ply/blob/66369a66fa85981ab7a5e1dffd4ff7109bf4fa54/src/ply/lex.py#L323-L330) consumes them.
</details>
# 答案2
**得分**: 1
那行代码实际上是该函数的文档（尽管其含义不太清晰）。它填充了函数本身的 `.__doc__` 属性。也许 `.__doc__` 属性在代码的其他地方被使用。
如果你写：
```python
def myFunc():
'这是我的函数，它始终返回3'
return 3
你将会得到：
print(myFunc.__doc__)
这是我的函数，它始终返回3
英文:
That line of code is actually documentation for the function (although its meaning isn't too clear). It populates the .__doc__ property of the function itself. Perhaps the .__doc__ property is used somewhere else in the code.
If you write:
def myFunc():
'This is my function, it always returns 3'
return 3
you will get:
print(myFunc.__doc__)
This is my function, it always returns 3
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