Question

I’m taking a csv file with a header line (called aggregate_file), sorting it by column, and re-writing it to another csv file (called sorted_file). The columns’ headings that I want to sort by are specified by variable_names.

def sortbyCounty(aggregate_file, sorted_file, *variable_names): 
    f = open(aggregate_file, 'r')
    readit = csv.reader(f) 
    headers = readit.next()
    col_indices = []
    for var in variable_names: 
         col_indices.append(headers.index(var))
    print col_indices
    thedata = list(readit)
    thedata.sort(key=operator.itemgetter(col_indices))
    fx = open(sorted_file, 'w') 
    writeit = csv.writer(fx)
    writeit.writerow(headers)
    writeit.writerows(thedata)
    writeit.close()
    return sorted_file

Next, I call this function in the following lines:

aggregate_file = "Aggregate_test90.csv"
sorted_file = "County_test90.csv"
variable_names = 'CTYCODE90'
test = sortbyCounty(aggregate_file, sorted_file, *variable_names)

Here is my error message:

col_indices.append(headers.index(var))
ValueError: list.index(x): x not in list

However, when I print my headers list, I can clearly see that my variable is present:

['_STATE90', 'HEIGHT90', 'WEIGHT90', '_BMI90', 'AGE90', 'CTYCODE90', 'IYEAR90', 'SEX90', '_RFOBESE90']

So I don’t understand why I’m receiving this error message at all. What am I missing?

Answer 1

variable_names should be a list or tuple of strings. As strings also behave like sequence, * on variable_names is turning your function call into this:

sortbyCounty(aggregate_file, sorted_file, 'C', 'T', 'Y', 'C', 'O', 'D', 'E', '9', '0')

When you clearly want the function call to be like this:

sortbyCounty(aggregate_file, sorted_file, 'CTYCODE90')

Making variable_names a list or tuple of strings should do it.