Pandas isna() 和 isnull()，有什么区别？
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Pandas isna() and isnull(), what is the difference?
提问by bakka
Pandas has both isna()and isnull(). I usually use isnull()to detect missing values and have never met the case so that I had to use other than that.
So, when to use isna()?
Pandas 有isna()和isnull()。我通常isnull()用来检测缺失值，但从未遇到过这种情况，因此我不得不使用其他方法。那么，什么时候使用isna()？
回答by qsantos
isnullis an alias for isna. Literally in the code source of pandas:
isnull是 的别名isna。从字面上看，在pandas的代码源中：
isnull = isna
Indeed:
的确：
>>> pd.isnull
<function isna at 0x7fb4c5cefc80>
So I would recommend using isna.
所以我会推荐使用isna.
回答by Tam Le
The documentation for both is literally identical.
两者的文档实际上是相同的。
pandas.isna() : https://pandas.pydata.org/pandas-docs/stable/generated/pandas.isna.html#pandas.isna
pandas.isna() : https://pandas.pydata.org/pandas-docs/stable/generated/pandas.isna.html#pandas.isna
pandas.isnull() : https://pandas.pydata.org/pandas-docs/stable/generated/pandas.isnull.html#pandas.isnull
pandas.isnull() : https://pandas.pydata.org/pandas-docs/stable/generated/pandas.isnull.html#pandas.isnull
In here, it even says DataFrame.isnull is an alias of isna in See also section.
在这里，它甚至说 DataFrame.isnull 是另见部分 isna 的别名。
pandas.DataFrame.isnull(): https://pandas-docs.github.io/pandas-docs-travis/generated/pandas.DataFrame.isnull.html#pandas.DataFrame.isnull
pandas.DataFrame.isnull(): https://pandas-docs.github.io/pandas-docs-travis/generated/pandas.DataFrame.isnull.html#pandas.DataFrame.isnull
Therefore, they must be the same thing, like np.nan, np.NaN, np.NAN.
因此，它们必须是相同的东西，例如 np.nan、np.NaN、np.NAN。
回答by Jyoti Prasad Pal
They both are same. As a best practice, always prefer to use isna()over isnull().
他们都是一样的。作为最佳实践，总是更喜欢使用isna()over isnull()。
It is easy to remember what isna()is doing because when you look at numpy method np.isnan(), it checks NaNvalues. In pandas there are other similar method names like dropna(), fillna()that handles missing values and it always helps to remember easily.
很容易记住isna()正在做什么，因为当您查看 numpy method 时np.isnan()，它会检查NaN值。在 Pandas 中，还有其他类似的方法名称，例如dropna()，fillna()用于处理缺失值，并且总是有助于轻松记住。
