Converting list output in Python

Question

I have a function that works as follows to read a .csv file and store it in an array.

def read_csv(self, filename, delimiter = ',', quotechar = '"'):
    reader = csv.reader(open(filename, 'rb'), delimiter = delimiter, quotechar = quotechar)
    # read first line and extract its data 
    self.column_headings = np.array(next(reader))
    # read subsequent lines
    rows = []
    for row in reader:
        rows.append(row)
    self.data = np.array(rows)
    self.m, self.n = self.data.shape

I'm simply trying to read a .tsv file so that it will return in the same form. I have this so far :

traindata = np.array(p.read_table('train.tsv'))[:,2]

However, when I try to call :

m, n = traindata.data.shape

# Display
print m, n, traindata.column_headings

I get the error :

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-14-1f877ccb37b5> in <module>()
----> 1 m, n = traindata.data.shape

AttributeError: 'buffer' object has no attribute 'shape'

What is causing this issue and how can I fix it ?

if you're reading a .tsv file (ie. a tab separated value file) should the delimiter not be '\t'? — superjump
– superjump, Commented Feb 9, 2014 at 21:06
@superjump The read_csv function is just for reading csv files, I'd like the tsv I am reading to be in the same format but cannot seem to call the print m, n, traindata.column_headings function :) — Simon Kiely
– Simon Kiely, Commented Feb 9, 2014 at 21:12

jonrsharpe · Accepted Answer · 2014-02-09 21:26:56Z

1

You explicitly create a list of traindata:

traindata = list(np.array(p.read_table('train.tsv'))[:,2])
          # ^ here

If you want to use it as a numpy.array, remove the list() call:

traindata = np.array(p.read_table('train.tsv'))[:,2]

Secondly, you want the shape of the array, not its data:

m, n = traindata.shape

edited Feb 9, 2014 at 21:26

answered Feb 9, 2014 at 20:56

jonrsharpe

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7 Comments

Simon Kiely Over a year ago

Oh. God. I need a coffee. Sorry, didn't mean to spam like this, you know sometimes how your eyes get crossed from coding too long?! Sorry again, thank you :)

jonrsharpe Over a year ago

You have changed the question, meaning my answer is no longer correct. However, I have added an answer to your second problem.

Simon Kiely Over a year ago

Thank you very much for this. It is unfortunately now returning the error --------------------------------------------------------------------------- ValueError Traceback (most recent call last) <ipython-input-10-e8668026004b> in <module>() ----> 1 m, n = traindata.shape ValueError: need more than 1 value to unpack however. Would you please be able to offer some guidance here?

jonrsharpe Over a year ago

It appears that your traindata is one-dimensional, so shape is a 1-tuple and can't be unpacked to two values.

Simon Kiely Over a year ago

This confuses me, as my traindata isn't one-dimensional. An extract of it I have uploaded here : pastebin.com/w9tc7tHZ and the full amount can be downloaded from kaggle.com/c/stumbleupon/data (train.tsv file). I don't understand why it should produce this error message, unless perhaps I am handling quotation marks incorrectly? Apologies for the nuisance here, but any help would be very much appreciated :)

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