Sorting a list: int object not callable

Question

I have a long and complicated method, I'll give the important parts:

def get_itter(self, sort_by=0): #sort_by is set to 0 for debugging purposes

    ...

    r = self.parser(self.in_file) # parse a csv file

    ...

    if type(sort_by) == int:
        r = [i for i in r]
        sort = sorted(r, key=sort_by)
    ...

Now my problem is that when I run this code it gives me an error: TypeError: 'int' object is not callable. Why is it giving me this error?

P.S. I am relatively new to Python and am trying to add some functionality to code that I did not write.

@MartijnPieters I have a csv file full of dates, and I need to sort the csv file by date. so that I can run it trough a custom parser and import the data to the system — Renier
– Renier, Commented Jan 30, 2014 at 14:47
And what is sort_by supposed to represent? The column number? — Martijn Pieters
– Martijn Pieters, Commented Jan 30, 2014 at 14:48
Then jonrsharpe's answer has got you covered; use itemgetter() as the sort key. And use isinstance(sort_by, int) instead of testing for a fixed type. — Martijn Pieters
– Martijn Pieters, Commented Jan 30, 2014 at 14:54

jonrsharpe · Accepted Answer · 2014-01-30 14:48:14Z

5

You set:

sort_by=0

check it's an int

if type(sort_by) == int: # note: isinstance(sort_by, int) is preferred here

then use it:

sorted(r, key=sort_by)

When you pass a key to sorted, it tries to apply that key to all items in the sequence it's sorting, trying to call it with each item, something like:

sortvalues = [key(i) for i in seq]

If key is an integer, you can't call it:

0(1)

gives the TypeError you are seeing.

It's not clear exactly what you're trying to do, but if you want to sort by the sort_byth item in a sequence, you can use operator.itemgetter:

from operator import itemgetter
sorted(r, key=itemgetter(sort_by))

edited Jan 30, 2014 at 14:48

answered Jan 30, 2014 at 14:41

jonrsharpe

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dornhege · Accepted Answer · 2014-01-30 14:42:21Z

1

You set sort_by to 0 and then pass that as the key function to sorted. Python will call key as a function to define the sorting key, which isn't possible for 0.

answered Jan 30, 2014 at 14:42

dornhege

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