Use Multiple Character Delimiter in Python Pandas read_csv

Question

It appears that the pandas read_csv function only allows single character delimiters/separators. Is there some way to allow for a string of characters to be used like, "*|*" or "%%" instead?

Answer 1

Pandas does now support multi character delimiters

import panda as pd
pd.read_csv(csv_file, sep="\*\|\*")

Answer 2

The solution would be to use read_table instead of read_csv:

1*|*2*|*3*|*4*|*5
12*|*12*|*13*|*14*|*15
21*|*22*|*23*|*24*|*25

So, we could read this with:

pd.read_table('file.csv', header=None, sep='\*\|\*')

Answer 3

As Padraic Cunningham writes in the comment above, it's unclear why you want this. The Wiki entry for the CSV Spec states about delimiters:

... separated by delimiters (typically a single reserved character such as comma, semicolon, or tab; sometimes the delimiter may include optional spaces),

It's unsurprising, that both the csv module and pandas don't support what you're asking.

However, if you really want to do so, you're pretty much down to using Python's string manipulations. The following example shows how to turn the dataframe to a "csv" with $$ separating lines, and %% separating columns.

'$$'.join('%%'.join(str(r) for r in rec) for rec in df.to_records())

Of course, you don't have to turn it into a string like this prior to writing it into a file.

Answer 4

Not a pythonic way but definitely a programming way, you can use something like this:

import re

def row_reader(row,fd):
    arr=[]
    in_arr = str.split(fd)
    i = 0
    while i < len(in_arr):
        if re.match('^".*',in_arr[i]) and not re.match('.*"$',in_arr[i]):
            flag = True
            buf=''
            while flag and i < len(in_arr):
                buf += in_arr[i]
                if re.match('.*"$',in_arr[i]):
                    flag = False
                i+=1
                buf += fd if flag else ''
            arr.append(buf)
        else:
            arr.append(in_arr[i])
            i+=1
    return arr

with open(file_name,'r') as infile:
    for row in infile:
        for field in  row_reader(row,'%%'):
            print(field)

Answer 5

In pandas 1.1.4, when I try to use a multiple char separator, I get the message:

ParserWarning: Falling back to the 'python' engine because the 'c' engine does not support regex separators (separators > 1 char and different from '\s+' are interpreted as regex); you can avoid this warning by specifying engine='python'.

Hence, to be able to use multiple char separator, a modern solution seems to be to add engine='python' in read_csv argument (in my case, I use it with sep='[ ]?;)