Drop columns whose name contains a specific string from pandas DataFrame
PythonPandasDataframePython Problem Overview
I have a pandas dataframe with the following column names:
Result1, Test1, Result2, Test2, Result3, Test3, etc...
I want to drop all the columns whose name contains the word "Test". The numbers of such columns is not static but depends on a previous function.
How can I do that?
Python Solutions
Solution 1 - Python
Here is one way to do this:
df = df[df.columns.drop(list(df.filter(regex='Test')))]
Solution 2 - Python
import pandas as pd
import numpy as np
array=np.random.random((2,4))
df=pd.DataFrame(array, columns=('Test1', 'toto', 'test2', 'riri'))
print df
Test1 toto test2 riri
0 0.923249 0.572528 0.845464 0.144891
1 0.020438 0.332540 0.144455 0.741412
cols = [c for c in df.columns if c.lower()[:4] != 'test']
df=df[cols]
print df
toto riri
0 0.572528 0.144891
1 0.332540 0.741412
Solution 3 - Python
Cheaper, Faster, and Idiomatic: str.contains
In recent versions of pandas, you can use string methods on the index and columns. Here, str.startswith seems like a good fit.
To remove all columns starting with a given substring:
df.columns.str.startswith('Test')
# array([ True, False, False, False])
df.loc[:,~df.columns.str.startswith('Test')]
toto test2 riri
0 x x x
1 x x x
For case-insensitive matching, you can use regex-based matching with str.contains with an SOL anchor:
df.columns.str.contains('^test', case=False)
# array([ True, False, True, False])
df.loc[:,~df.columns.str.contains('^test', case=False)]
toto riri
0 x x
1 x x
if mixed-types is a possibility, specify na=False as well.
Solution 4 - Python
This can be done neatly in one line with:
df = df.drop(df.filter(regex='Test').columns, axis=1)
Solution 5 - Python
You can filter out the columns you DO want using 'filter'
import pandas as pd
import numpy as np
data2 = [{'test2': 1, 'result1': 2}, {'test': 5, 'result34': 10, 'c': 20}]
df = pd.DataFrame(data2)
df
c result1 result34 test test2
0 NaN 2.0 NaN NaN 1.0
1 20.0 NaN 10.0 5.0 NaN
Now filter
df.filter(like='result',axis=1)
Get..
result1 result34
0 2.0 NaN
1 NaN 10.0
Solution 6 - Python
Use the DataFrame.select method:
In [38]: df = DataFrame({'Test1': randn(10), 'Test2': randn(10), 'awesome': randn(10)})
In [39]: df.select(lambda x: not re.search('Test\d+', x), axis=1)
Out[39]:
awesome
0 1.215
1 1.247
2 0.142
3 0.169
4 0.137
5 -0.971
6 0.736
7 0.214
8 0.111
9 -0.214
Solution 7 - Python
Using a regex to match all columns not containing the unwanted word:
df = df.filter(regex='^((?!badword).)*$')
Solution 8 - Python
This method does everything in place. Many of the other answers create copies and are not as efficient:
df.drop(df.columns[df.columns.str.contains('Test')], axis=1, inplace=True)
Solution 9 - Python
Question states 'I want to drop all the columns whose name contains the word "Test".'
test_columns = [col for col in df if 'Test' in col]
df.drop(columns=test_columns, inplace=True)
Solution 10 - Python
the shortest way to do is is :
resdf = df.filter(like='Test',axis=1)
Solution 11 - Python
Solution when dropping a list of column names containing regex. I prefer this approach because I'm frequently editing the drop list. Uses a negative filter regex for the drop list.
drop_column_names = ['A','B.+','C.*']
drop_columns_regex = '^(?!(?:'+'|'.join(drop_column_names)+')$)'
print('Dropping columns:',', '.join([c for c in df.columns if re.search(drop_columns_regex,c)]))
df = df.filter(regex=drop_columns_regex,axis=1)