Remove ends of string entries in pandas DataFrame column

问题

I have a pandas Dataframe with one column a list of files

import pandas as pd
df = pd.read_csv('fname.csv')

df.head()

filename    A    B    C
fn1.txt   2    4    5
fn2.txt   1    2    1
fn3.txt   ....
....

I would like to delete the file extension .txt from each entry in filename. How do I accomplish this?

I tried:

df['filename'] = df['filename'].map(lambda x: str(x)[:-4])

but when I look at the column entries afterwards with df.head(), nothing has changed.

How does one do this?

回答1:

I think you can use str.replace with regex .txt$' ( $ - matches the end of the string):

import pandas as pd

df = pd.DataFrame({'A': {0: 2, 1: 1}, 
                   'C': {0: 5, 1: 1}, 
                   'B': {0: 4, 1: 2}, 
                   'filename': {0: "txt.txt", 1: "x.txt"}}, 
                columns=['filename','A','B', 'C'])

print df
  filename  A  B  C
0  txt.txt  2  4  5
1    x.txt  1  2  1

df['filename'] = df['filename'].str.replace(r'.txt$', '')
print df
  filename  A  B  C
0      txt  2  4  5
1        x  1  2  1

df['filename'] = df['filename'].map(lambda x: str(x)[:-4])
print df
  filename  A  B  C
0      txt  2  4  5
1        x  1  2  1

df['filename'] = df['filename'].str[:-4]
print df
  filename  A  B  C
0      txt  2  4  5
1        x  1  2  1

EDIT:

rstrip can remove more characters, if the end of strings contains some characters of striped string (in this case ., t, x):

Example:

print df
  filename  A  B  C
0  txt.txt  2  4  5
1    x.txt  1  2  1

df['filename'] = df['filename'].str.rstrip('.txt')

print df
  filename  A  B  C
0           2  4  5
1           1  2  1

回答2:

You can use str.rstrip to remove the endings:

df['filename'] = df['filename'].str.rstrip('.txt')

should work

回答3:

You may want:

df['filename'] = df.apply(lambda x: x['filename'][:-4], axis = 1)

回答4:

use list comprehension

df['filename'] = [x[:-4] for x in df['filename']]

来源：https://stackoverflow.com/questions/37001787/remove-ends-of-string-entries-in-pandas-dataframe-column

标签

python

pandas

dataframe

string-matching