regex case insensitive filtering of columns in pandas

Question

I am trying to match a string(column) in csv files in python using Python but it does not match anything. I want the string to be match to be case insensitive. I am quite new but this is what I tried to do

test = pd.read_csv("data.csv")
mytest= pd.DataFrame(test, columns=[re.search("[a-zA-Z1-9_]", "columnname1", re.IGNORECASE),])
print(mytest)

Any help will be highly appreciated

Answer 1

If I understand what you're after you can filter your df to only return the columns where the name matches and make it case-insensitive:

In [298]:

df = pd.DataFrame({'columnname1':np.arange(5), 'ColumnName1':np.arange(5), 'columnname2':0, 'column name 1':0})
df
Out[298]:
   ColumnName1  column name 1  columnname1  columnname2
0            0              0            0            0
1            1              0            1            0
2            2              0            2            0
3            3              0            3            0
4            4              0            4            0

In [299]:

import re
df.filter(regex=re.compile("columnname1", re.IGNORECASE))
Out[299]:
   ColumnName1  columnname1
0            0            0
1            1            1
2            2            2
3            3            3
4            4            4

EDIT

For matching just the name without words preceding it, so matching on 'Test' but not 'My Test':

In [52]:

df = pd.DataFrame({'Test':np.arange(5), 'ColumnName1':np.arange(5), 'My Test':0, 'My column name 1':0})
import re
df.filter(regex=re.compile(r"^Test$", re.IGNORECASE))
Out[52]:
   Test
0     0
1     1
2     2
3     3
4     4

So the ^ looks for 'Test' at the beginning of the str and the $ marks the end of the pattern to search, there is a handy cheat sheet .