[英]Get list of column names all values are NaNs in Python
Can I use Python to get a list of the column names in which all values are NaN
s, return c
and d
as result from dataframe below?我可以使用 Python 获取所有值都是
NaN
的列名列表,从下面的数据帧返回c
和d
作为结果吗? Thanks.谢谢。
df = pd.DataFrame({'a': [1,2,3],'b': [3,4,5], 'c':[np.nan, np.nan, np.nan],
'd':[np.nan, np.nan, np.nan]})
a b c d
0 1 3 NaN NaN
1 2 4 NaN NaN
2 3 5 NaN NaN
Use Boolean indexing with df.columns
:对
df.columns
使用布尔索引:
res = df.columns[df.isnull().all(0)]
# Index(['c', 'd'], dtype='object')
@ahbon , you can try df.any()
. @ahbon ,你可以试试
df.any()
。 See the following sequence of statements executed on Python's interactive terminal.请参阅以下在 Python 交互式终端上执行的语句序列。
Check http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.any.html
检查http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.any.html
>>> import numpy as np
>>> import pandas as pd
>>>
>>> df = pd.DataFrame({'a':[1,2,3],'b':[3,4,5],'c':[np.nan, np.nan, np.nan],'d':[np.nan, np.nan, np.nan]})
>>> df
a b c d
0 1 3 NaN NaN
1 2 4 NaN NaN
2 3 5 NaN NaN
>>>
>>> # Remove all columns having all NaN values using DataFrame.any()
...
>>> df_new = df.any()
>>> df_new
a True
b True
c False
d False
dtype: bool
>>>
Finally,最后,
>>> columns = []
>>>
>>> for key, value in df_new.iteritems():
... if value:
... columns.append(key)
...
>>> df = pd.DataFrame({'a':[1,2,3],'b':[3,4,5],'c':[np.nan, np.nan, np.nan],'d':[np.nan, np.nan, np.nan]}, columns=columns)
>>>
>>> df
a b
0 1 3
1 2 4
2 3 5
>>>
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