Numpy(Pandas)删除全为零的列的方法
在处理numpy数组，有这个需求，故写下此文：
使用np.argwhere和np.all来查找索引。要使用np.delete删除它们。
示例1
importnumpyasnp a=np.array([[1,2,0,3,0], [4,5,0,6,0], [7,8,0,9,0]]) idx=np.argwhere(np.all(a[...,:]==0,axis=0)) a2=np.delete(a,idx,axis=1) print(a2) """ [[123] [456] [789]] """
示例2
importnumpyasnp
array1=np.array([[1,0,1,0,0,0,0,0,0,1,1,0,0,0,1,1,0,1,0,0],
[0,1,1,0,0,1,1,1,1,0,0,0,1,0,1,0,0,1,1,1],
[0,0,1,0,0,1,1,1,0,0,0,0,0,0,0,1,0,0,1,1],
[0,1,1,0,0,1,1,1,1,0,1,1,1,0,0,1,0,0,1,1],
[0,0,1,0,0,1,1,1,0,1,0,1,1,0,1,1,0,0,1,0],
[1,0,1,0,0,0,1,0,0,1,1,1,1,0,1,1,0,0,1,0],
[1,0,1,0,1,1,0,0,0,0,1,0,0,0,1,0,0,0,1,1],
[0,1,0,0,1,0,0,0,1,0,1,1,1,0,1,0,0,1,1,0],
[0,1,0,0,1,0,0,1,1,0,1,1,1,0,0,1,0,1,0,0],
[1,0,0,0,0,1,0,1,0,0,0,1,1,0,0,1,0,1,0,0]])
mask=(array1==0).all(0)
column_indices=np.where(mask)[0]
array1=array1[:,~mask]
print("rawarray",array1.shape)#rawarray(10,20)
print("afterarray",array1.shape)#afterarray(10,17)
print("=====x=====\n",array1)
其它查看：https://moonbooks.org/Articles/How-to-remove-array-rows-that-contain-only-0-in-python/
pandas删除全零列
frompandasimportDataFrame df1=DataFrame(np.arange(16).reshape((4,4)),index=['a','b','c','d'],columns=['one','two','three','four'])#创建一个dataframe df1.loc['e']=0#优雅地增加一行全0 df1.ix[(df1==0).all(axis=1),:]#找到它 df1.ix[~(df1==0).all(axis=1),:]#删了它
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