Find all the numbers in one file that are not in another file in python

Question

There are two files, say FileA and FileB and we need to find all the numbers that are in FileA which is not there in FileB. All the numbers in the FileA are sorted and all t

Answer 1

A simple solution based on file reading (asuming that each line hold a number):

results = []
with open('file1.csv') as file1, open('file2.csv') as file2:
        var1 = file1.readline()
        var2 = file2.readline()
        while var1:
            while var1 and var2:
                if int(var1) < int(var2):
                    results.append(int(var1))
                    var1 = file1.readline()
                elif int(var1) > int(var2):
                    var2 = file2.readline()
                elif int(var1) == int(var2):
                    var1 = file1.readline()
                    var2 = file2.readline()
            if var1:
                results.append(int(var1))
                var1 = file1.readline()
print(results)
output = [2, 5, 7, 9]