PyCharm 类型检查器预期类型为“无"，在使用 Pandas dataframe.to_csv 时改为“str" [英] PyCharm type checker expected type 'None', got 'str' instead when using pandas dataframe.to_csv

问题描述

使用 PyCharm 2021.2(社区版)和 Pandas 1.3.1，代码如下:

Using PyCharm 2021.2 (Community Edition) and Pandas 1.3.1, with the following code:

import pandas as pd
d = {'col1': [1, 2], 'col2': [3, 4]}
df = pd.DataFrame(data=d)
df.to_csv("testfile.csv")

PyCharm 将产生警告，突出显示testfile.csv"，并显示Expected type 'None', got 'str' instead"将鼠标悬停在警告上方时.

PyCharm will produce a Warning, highlight "testfile.csv", and display "Expected type 'None', got 'str' instead" when hovering over the Warning.

testfile.csv 已创建，似乎没有发生任何问题.

testfile.csv is created and no issues appear to be happening.

有没有办法解决这个问题?有谁知道为什么会出现这个警告?

Is there a way to fix this? Does anyone know why this Warning appears?

谢谢

推荐答案

这似乎是 Pycharm 中的一个错误，导致它无法正确解释 |；typing.Union 的新运算符.

This appears to be a bug in Pycharm that prevents it from properly interpreting |; the new operator for typing.Union.

如果我 ctrl+p 而在 to_csv 的参数列表中，我得到这个

If I ctrl+p while inside of the argument list of to_csv, I get this

注意，它认为参数是 None 类型(由 : None 表示).

Note that it thinks the argument is of type None (indicated by : None).

问题是，这是函数的实际签名:

The problem is, this is the actual signature of the function:

def to_csv(
           self,
           path_or_buf: FilePathOrBuffer[AnyStr] | None = None,
           . . .

参数的类型实际上是FilePathOrBuffer[AnyStr] |无，在 Python 3.10 之前将是 typing.Union[FilePathOrBuffer[AnyStr], None] 或简单的 typing.Optional[FilePathOrBuffer[AnyStr]].

The type of the parameter is actually FilePathOrBuffer[AnyStr] | None, which prior to Python 3.10 would be typing.Union[FilePathOrBuffer[AnyStr], None] or simply typing.Optional[FilePathOrBuffer[AnyStr]].

Pycharm 显然还不能读取花哨的类型提示，尽管它说它支持 Python 3.10.

Pycharm apparently can't yet read fancy type hints, despite saying it supports Python 3.10.

这篇关于PyCharm 类型检查器预期类型为“无"，在使用 Pandas dataframe.to_csv 时改为“str"的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！