python error reading a csv file

Question

with open('repo-attributes.csv', 'rb') as repofile:
    reader = csv.DictReader(repofile)
    for repo in reader:
        g.add_vertex(name=repo['repository_url'],
            label=repo['repository_url'][19:],
            language='(unknown)' if repo['repository_language'] == 'null'
                else repo['repository_language'],
            watchers=int(repo['repository_watchers']))

This is my code. I am getting the error like as follows. I am new to python. kindly explain this.

Traceback (most recent call last):
  File "C:\Python34\github-network-analysis-master\process.py", line 9, in <module>
    for repo in reader:
  File "C:\Python34\lib\csv.py", line 109, in __next__
    self.fieldnames
  File "C:\Python34\lib\csv.py", line 96, in fieldnames
    self._fieldnames = next(self.reader)
_csv.Error: iterator should return strings, not bytes (did you open the file in text mode?)

The error is self explanatory really. You opened a file with rb flag, which means open in read binary mode. You only want r flag which is just read. — ljetibo
– ljetibo, Commented Feb 23, 2015 at 14:52
Using 'rb' is the correct thing to do when running Python 2; in Python 3 the advice in the module documentation is to use 'r' and newline=''. — Martijn Pieters
– Martijn Pieters, Commented Feb 23, 2015 at 15:27
Perhaps relevant here: How can I stop Python's csv.DictWriter.writerows from adding empty lines between rows in Windows? — Martijn Pieters
– Martijn Pieters, Commented Feb 23, 2015 at 15:34

Padraic Cunningham · Accepted Answer · 2015-02-23 15:36:52Z

3

Remove b, you are opening in binary mode hence the bytes error:

 with open('repo-attributes.csv', newline="") as repofile:

You can actually remove both as the default mode is r.

edited Feb 23, 2015 at 15:36

answered Feb 23, 2015 at 14:52

Padraic Cunningham

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4 Comments

Martijn Pieters Over a year ago

The OP should add newline='' as well. See the csv.reader() documentation. They most likely read posts about using csv.reader() with Python 2, where using 'rb' is recommended.

Padraic Cunningham Over a year ago

@MartijnPieters, I don't see anything related to newline when dealing with DictReader

Padraic Cunningham Over a year ago

@MartijnPieters, what is the deal with newline="" I don't ever remember using it? Basically universal newlines?

Martijn Pieters Over a year ago

How can I stop Python's csv.DictWriter.writerows from adding empty lines between rows in Windows? Yes, newline='' stops the file object from translating newlines for you, so the CSV reader can distinguish between embedded newlines and row separators.

NPatel · Accepted Answer · 2015-02-23 14:54:23Z

0

You are opening file in rb means read binary please open it in read mode. change your code to

...
...
with open('repo-attributes.csv', 'r')...
...
...

This will open file in read mode (not binary).

answered Feb 23, 2015 at 14:54

NPatel

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Comments

rahulmishra · Accepted Answer · 2015-02-23 14:55:28Z

0

The last line of the trace tells where the error first occurred. Since you opened the file in binary mode, python is reading bytes. Your file is csv and opening it in read mode will suffice.

So instead of rb use r

answered Feb 23, 2015 at 14:55

rahulmishra

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