"IOError: [Errno 0] Error" error in Python

Question

I have a script that should append something to a file, but it is raising an error that I don't understand and not sure how it is being triggered.

Here is the code:

import re

num_words = "four kiddiewinks|four children|four kids"
words_list = num_words.split('|')

def append_2synonym(words_list, num_words):
    with open('test2 words.txt', 'a+') as f:
        read_f = f.read()
        patt = r'^' + words_list[0] + '\|'
        result = re.search(patt, read_f, re.MULTILINE)
        if result == None:
            f.write("\n" + num_words)
        else:
            print "\nNo match found in '2 words.txt' file"

append_2synonym(words_list, num_words)

Here is the contents of the 'test2 words.txt' file:

five kiddiewinks|five kids|five children
mobile phone|cell phone|cellular phone
stinky cheese|smelly cheese

Here is the full error I am getting:

Traceback (most recent call last):
  File "D:\Magic Briefcase\My Python Scripts\Spin Scripts\synonyms\testing2.py", line 16, in <module>
    append_2synonym(words_list, num_words)
  File "D:\Magic Briefcase\My Python Scripts\Spin Scripts\synonyms\testing2.py", line 12, in append_2synonym
    f.write("\n" + num_words)
IOError: [Errno 0] Error
[Finished in 0.1s with exit code 1]

Looks similar to stackoverflow.com/questions/11176724/python-file-operations, are you on Windows? — Benjamin Toueg
– Benjamin Toueg, Commented Oct 9, 2013 at 21:37

Community · Accepted Answer · 2017-05-23 12:00:07Z

9

Quoting answer from Python file operations, when switching between reading and writing on Windows, there must be an intervening fflush, fsetpos, fseek, or rewind operation.

Here is a possible fix:

import re

num_words = "four kiddiewinks|four children|four kids"
words_list = num_words.split('|')

def append_2synonym(words_list, num_words):
    with open('test2 words.txt', 'a+') as f:
        read_f = f.read()
        patt = r'^' + words_list[0] + '\|'
        result = re.search(patt, read_f, re.MULTILINE)
        if result == None:
            f.seek(0,2) # change is here !!
            f.write("\n" + num_words)
        else:
            print "\nNo match found in '2 words.txt' file"

append_2synonym(words_list, num_words)

In f.seek(0,2), 2 is the from_what argument. A from_what value of 0 measures from the beginning of the file, 1 uses the current file position, and 2 uses the end of the file as the reference point. from_what can be omitted and defaults to 0, using the beginning of the file as the reference point.

edited May 23, 2017 at 12:00

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answered Oct 9, 2013 at 21:40

Benjamin Toueg

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4 Comments

torek Over a year ago

Since f.read() reads to EOF, the original should work: the C standard allows switching from read to write mode if read encounters EOF. If this does fix it, that implies the C library on (some compilers and/or some versions of?) Windows gets this wrong.

Darren Haynes Over a year ago

@btoueg - thanks this is working. I tried it several times and the apeending keeps working and growing the 'test2 words.txt' file. I just tried looking at the python docs about .seek(), but I could not totally figure out f.seek(0,2). I understand that the first argument 0 effectively rewinds to the beginning of the file, but what is the 2 doing?

Benjamin Toueg Over a year ago

I've edited the answer. For more details, go check the answer I am referring to.

Darren Haynes Over a year ago

Thank you. I will now study that answer in more details. I appreciate the help :-)

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