Find delimiter in txt to convert to csv using Python

You have to use dialect.delimiter instead of just dialect because what is returned is of type class Dialect and you need its attribute Dialect.delimiter

rows=csv.reader(f1, delimiter=dialect.delimiter)

Modified code will be as below

import csv

filename_input = 'filein.txt'
filename_output = 'fileout.csv'
with open(filename_input, 'r') as f1, open(filename_output, 'wb') as f2:
    dialect = csv.Sniffer().sniff(f1.read(1024), "\t") #### detect delimiters
    f1.seek(0)
    print(dialect.delimiter)
    rows=csv.reader(f1, delimiter=dialect.delimiter)
    writer = csv.writer(f2,delimiter=';')
    writer.writerows(rows)

Output:

C:\pyp>python.exe txttocsv.py
,
C:\pyp>

Also note that from doc:

sniff(sample, delimiters=None)

Analyze the given sample and return a Dialect subclass reflecting the parameters found. If the optional delimiters parameter is given, it is interpreted as a string containing possible valid delimiter characters.

Hence if the delimiter that you want to find in your text file is something like # instead of , or ; then you should mention that in sniff function as second parameter like this:

dialect = csv.Sniffer().sniff(f1.read(1024), '#') 

Update: For reading whole file you will need

dialect = csv.Sniffer().sniff(f1.read())