python regex for filename

Question

I am trying to do a regex on a dataframe.

For example a value will be ia wt template - tdct-c15-c5.doc The best logic I can think of is to take everything after the - till the last digit in the string.

trying to trim it to tdct-c15-c5

any help would be appreciated.

If this example has the same structure as any other value that you need to trim, I would recommend you that just split by whitespaces the value and get the last position. Otherwise a regex I am not sure how it could help you unless you give more information. — Jorge Machado
– Jorge Machado, Commented Feb 3, 2022 at 19:32

hc_dev · Accepted Answer · 2022-02-03 21:27:57Z

2

Components

To stay flexible, assume your input filename(s) contain chunks:

filenames with fix extension .doc (denoting Word files or documents)
some important key (here tdct-c15-c5)
the separator as hyphen possibly surrounded by spaces (here surrounded by spaces -)
some prefix, does not matter currently (here ia wt template)

This information is contained inside ia wt template - tdct-c15-c5.doc.

Decomposition steps

Particularly the chunks (1) and (3) seem pretty stable and fixed constants. So lets work with them:

we can strip-off from right or remove the extension (1) as ignored
we can split the remaining basename by separator (3) into 2 parts: prefix (4) and key (2)

The last part (2) is what we want to extract.

Implementation (pure Python only)

def extract_key(filename):
    basename = filename.rstrip('.doc')
    (prefix, key) = basename.split(' - ')  # or use lenient regex r'\ ?-\ ?'
    return key


filename = 'ia wt template - tdct-c15-c5.doc'
print('extracted key:', extract_key(filename))

Prints:

('extracted key:', 'tdct-c15-c5')

Applied to pandas

Use the function as suggested by C.Nivis inside apply():

df.apply(extract_key)

edited Feb 3, 2022 at 21:27

answered Feb 3, 2022 at 21:21

hc_dev

9,6941 gold badge30 silver badges47 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Jonnyboi Over a year ago

Thanks, say I have a dataframe like : df.filename , how do I loop through each row with your function? and store into a new column?

hc_dev Over a year ago

@Jonnyboi, this assumptive dataframe df.filename and the question how to add a new column based on the extracted key is not part of your question. Please also research as instructed in How to Ask, e.g. search SO for [pandas] new column based on other column Would you like to add it there first?

C.Nivs · Accepted Answer · 2022-02-03 21:02:54Z

1

I don't know if a regex is the better option here. An apply is pretty readable:

mystr = "ia wt template - tdct-c15-c5.doc"
import pandas as pd

df = pd.DataFrame([[mystr] for i in range(4)], columns=['mystr'])

df.mystr.apply(lambda x: x.split(' ')[-1].rstrip('.doc'))
0    tdct-c15-c5
1    tdct-c15-c5
2    tdct-c15-c5
3    tdct-c15-c5
Name: mystr, dtype: object

answered Feb 3, 2022 at 21:02

C.Nivs

13.2k3 gold badges21 silver badges48 bronze badges

Collectives™ on Stack Overflow

python regex for filename

2 Answers 2

Components

Decomposition steps

Implementation (pure Python only)

Applied to pandas

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Components

Decomposition steps

Implementation (pure Python only)

Applied to pandas

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related