Python: Compare List with a List in File

Question

I am strugling with this problem that looks simple but I'm stuck! Well, I have to build a function where I receive a list of categories like:

input Example1: ['point_of_interest', 'natural_feature', 'park', 'establishment']
input Example2: ['point_of_interest', 'establishment']
input Example3: ['sublocality', 'political']

So that list could be with variable elements inside I guess from 1 till 4 not more

So with this same data I am gonna create a file with that input in a way that if the new input is not in the file, append it to the file .

The way is each list is an element itself, I mean I have to compare the full elements of the list and if I can find other list exactly equal I don´t have to add it.

In my code I just tried to add the first element in the file because really I don't know how to add the full list to compare with the next list.

def categories(category):
    number = 0
    repeat = False
    if os.path.exists("routes/svm/categories"):
        with open('routes/svm/categories', 'rb') as csvfile:
            spamreader = csv.reader(csvfile)
            for categoryFile in spamreader:
                if (cmp(categoryFile,category) == 0):
                    number += 1
                    repeat = True
                if not repeat:
                    categoriesFile = open('routes/svm/categories', 'a') 
                    category = str(category[0])     
                    categoriesFile.write(category) 
                    categoriesFile.write('\n')
                    categoriesFile.close()
                else:
                    categoriesFile = open('routes/svm/categories', 'w')
                    category = str(category[0])     
                    categoriesFile.write(category)
                    categoriesFile.write('\n')
                    categoriesFile.close()      

EDIT: Some explanation by @KlausWarzecha: Users might enter a list with (about 4) items. If this list ( = this combination of items) is not in the file already, you want to add the list (and not the items separately!) to the file? –

Answer 1

The problem is really simple. You may take the following approach if it works for you:

1. Read all the contents of the CSV into a list
2. Add all the non-matching items from the input into this list
3. re-write the CSV file

You may start with this sample code:

# input_list here represents the inputs
# You may get input from some other source too
input_list = [['point_of_interest', 'natural_feature', 'park', 'establishment'], ['point_of_interest', 'establishment'], ['sublocality', 'political']]
category_list = []
with open('routes/svm/categories', 'rb') as csvfile:
    spamreader = csv.reader(csvfile)
    for categoryFile in spamreader:
        print categoryFile
        category_list.append(categoryFile)
for item in input_list:
    if (item in category_list):
        print "Found"
    else:
        category_list.append(item)
        print "Not Found"

# Write `category_list` to the CSV file

Please use this code as a starting point and not as a copy-paste solution.