## Numpy (PANDAS) removes all zero columns

SongpingWang 2020-11-13 11:05:09
numpy pandas removes zero columns

Processing numpy Array , There is a need , So write this article ：

Use `np.argwhere` and `np.all` To find the index . To use `np.delete` Delete them .

Example 1

``````import numpy as np
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)
"""
[[1 2 3]
[4 5 6]
[7 8 9]]
"""
``````

Example 2

``````import numpy as np
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]])
print("raw array", array1.shape) # raw array (10, 20)
print("after array",array1.shape) # after array (10, 17)
print("=====x=====\n",array1)
``````

pandas Delete all zero Columns

``````from pandas import DataFrame
df1=DataFrame(np.arange(16).reshape((4,4)),index=['a','b','c','d'],columns=['one','two','three','four']) # Create a dataframe
df1.loc['e'] = 0 # Gracefully add a whole line 0
df1.ix[(df1==0).all(axis=1), :] # Find it
df1.ix[~(df1==0).all(axis=1), :] # Delete it
``````