Split CSV with python based on regex findings

Question

I am a python beginner and need your help. I need to split columns in a CSV on certain places which I find with regex. Split applied to CSV produces errors. Besides, some findings are not equal distributed in the columns.

The structure of CSV is like this:

a; b; c; 
d; e, f, g; h
i; j,e; k

I need to split after every e and to transform the CSV like this:

a;  ; b; c;
d; e; f, g; h
i; j; e; k

I have this code :

import csv
import re
r = re.compile("r'....\(...\)")
with open('test.csv', 'r') as csvfile:
  reader = csv.reader(csvfile, delimiter=';')
  your_list = list(reader)
your_list=r.split(your_list)    
print(your_list)

I'm getting this error :

TypeError: expected string or bytes-like object

the structure of your CSV is strange, is you "comma" a comma or a semicolon? — Nullman
– Nullman, Commented Mar 28, 2019 at 12:06
I'm not clear how you would get from your input example to your expected result by 'splitting on e'. It looks like you have inserted a blank between a and b, and changed the comma between j and e into a semicolon? — Adam T
– Adam T, Commented Mar 28, 2019 at 12:12
yes the structure is with custom denominator (;). comma is comma, semicolon separates columns. This is exactly the challenge due to strange structure. Yes, I added an additional ; between a and b in order to show that I will have an additional column after split. — Stanis
– Stanis, Commented Mar 28, 2019 at 12:22

Christoph Burschka · Accepted Answer · 2019-03-28 12:50:06Z

1

Not sure if this is the correct approach, but your specific error comes from trying to pass a list of strings to the regex matcher. You'll need to pass it each string separately.

Instead of

your_list = list(reader)
your_list=r.split(your_list)

Write

your_list=[r.split(x) for x in reader]

Edit: Never mind, this answer assumed that reader was a file handle rather than a CSV reader.

The CSV reader returns an iterable of iterables. I now suspect this is not the right approach, but if you want to split each cell of the CSV, you need to write

your_list=[
    [r.split(cell) for cell in row]
    for row in reader
]

edited Mar 28, 2019 at 12:50

answered Mar 28, 2019 at 12:20

Christoph Burschka

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3 Comments

Stanis Over a year ago

Thanks. But I get this error File "main_python_csv.py", line 9, in <module> your_list=[r.split(x) for x in reader] File "main_python_csv.py", line 9, in <listcomp> your_list=[r.split(x) for x in reader] TypeError: expected string or bytes-like object

Christoph Burschka Over a year ago

Fixed; an extra loop is required as the CSV reader returns a list of lists.

Stanis Over a year ago

Yes great, it worked. The splitting is still not working like expected, but it is close to it

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