Python Error io.UnsupportedOperation: not readable

Question

i have this error and i don't know why i got it. I followed the steps from my Python manual and i got this. I am tryng to cleanup the file on column 8 and 9 if they have that odd character. If someone could help me, please advise.

The error appear on the line of code: for row in csv.reader(f):

Please find below my code:

    import csv


file = '/Users/cohen/Desktop/sdn-2.csv'
newstring = "null"
newinteger = int(0)
with open(file, 'r+') as f:
    for row in csv.reader(f):
       if row[7] =="-0-":
           row[7] = newinteger
       if row[8] == "-0-":
           row[8] = newinteger
f.close()

***LATER EDIT I changed the code as above, but is not doing anything is not replacing the -0- with 0

`open(file, 'w')` You opened the file for writing, not reading. — John Gordon, Sep 08 '17 at 17:35
Even if you fix the `open` error, you still have an overall logic problem -- assigning to a row does _not_ write that change back to the file. — John Gordon, Sep 08 '17 at 17:44
It's probably best to read the data, clean up the csv rows as needed, write the cleaned rows to a new file, then delete the original file and rename the new file to the original name. — John Gordon, Sep 08 '17 at 18:02
Possible duplicate of [Python error message io.UnsupportedOperation: not readable](https://stackoverflow.com/questions/44901806/python-error-message-io-unsupportedoperation-not-readable) — flaviut, Aug 25 '18 at 11:54

score 0 · Answer 1 · answered Sep 08 '17 at 17:36

EDIT:

You need to open the file with r+. Using w is for write only, r+ is for both write and read access.

with open(file, 'r+') as f:

Using == as in row[7] == newinteger is calling the equality operator. It checks if the left and right operand's values are the same. You want to be setting the new value with =.

row[7] = newinteger

score 0 · Answer 2 · answered Sep 08 '17 at 17:38

The other stuff that those before me said too but I think this error is from the parentheses around the string "-0-". And maybe the space on the first use as well.

if row[7] ==("-0-"):

should be: if row[7] == "-0-":

if row[8] == ("-0-"):

should be: if row[8] == "-0-":

score 0 · Answer 3 · answered Sep 09 '17 at 21:11

This was my solution: to create an output file and to write in it, what i read from the source file. Is a bit odd, as in VBA was even easier to do this, then in python, but this is the solution within the csv module from pythn. I dont like that i have to create another file, and i can't basicaly write inside the readed file, and i have to write into a brand new file, but this is life....If someone has a better approach, I am opened to new.

Hope that others will use this code.

import csv
newstring = "null"
newinteger = (0)
with open('/Users/cohen/Desktop/sdn-4 2.csv', 'r') as file1, open('/Users/cohen/Desktop/new_sdn.csv', 'w', newline='') as file2:
    reader = csv.reader(file1, delimiter=',')
    writer = csv.writer(file2, delimiter=',')

    for row in reader:
        replaced1 = row[7].replace('-0-', newstring)
        row[7]=replaced1
        replaced2 = row[8].replace('-0-', newinteger)
        row[8]=replaced2
        writer.writerow(row)

Python Error io.UnsupportedOperation: not readable

3 Answers3