Loop thru text file and compare two lines

Question

Hi, I´m trying to read from a file, and then see if 2 Lines in there are equal if so then break the while loop. I cant recive the information from line2. In other words if line1==line2. In anywhere in the file.

example: line1 = [0,2,3,5,6], line2=[0,2,3,5,6]

I have used the readin code in a another file, and works like a charm. But not in here don´t know why. Please guys help me out.

while gameSet <26:


    cardList.sort()
    cardList = [card for card in cardList if card];
    for i in range(len(cardList)):
        cardList.sort();
        cardList[i]-=1;
        newHeap = len(cardList);

    cardList.append(newHeap);        
    print gameSet, ": cardList in loop: ", cardList;
    forfile = str(cardList);

    #Put output to file
    fileName = "file13.txt";
    inFile = open(fileName, "a")
    for i in range(1):
        add = (str(forfile)+"\n");
        inFile.write(str(add));
    inFile.close();

    #Read file and compare
    inFile=open(fileName)
    while True:
        line1 = inFile.readline()
        line2 = inFile.readline()
        if not line2: break
    print "line1: ",line1,"line2: ",line2
    if (line1==line2) & (line1!="") & (line2!="") :
        break 
    inFile.close;
    gameSet +=1;

This is the output:

Game starts with this:[5.0, 5.0] 1 : cardList in loop: [4.0, 4.0, 2] line1: [4.0, 4.0, 2] line2:
2 : cardList in loop: [1, 3.0, 3.0, 3] line1: line2:
3 : cardList in loop: [0, 2.0, 2.0, 2, 4] line1: [0, 2.0, 2.0, 2, 4] line2:
4 : cardList in loop: [1.0, 1.0, 1, 3, 4] line1: line2:
5 : cardList in loop: [0.0, 0.0, 0, 2, 3, 5] line1: [0.0, 0.0, 0, 2, 3, 5] line2:
6 : cardList in loop: [1, 2, 4, 3] line1: line2:
7 : cardList in loop: [0, 1, 2, 3, 4] line1: [0, 1, 2, 3, 4] line2:
8 : cardList in loop: [0, 1, 2, 3, 4] line1: line2:
9 : cardList in loop: [0, 1, 2, 3, 4] line1: [0, 1, 2, 3, 4] line2:
cardList: [0, 1, 2, 3, 4]

Answer 1

Let's see the inner while loop:

while True:
    line1 = inFile.readline()
    line2 = inFile.readline()
    if not line2: break

It uses the readline method, which also reads in the newline character(s) depending on your platform. So this loop will terminate only at the end of the file. Depending on the number of lines in your file it will result in two empty strings (in the case of even number of total lines) or the last single line (in the case of odd number of total lines). For example:

• Even number of lines:

  A
  B
  C
  D
  

It will result in line1 == '' and line2 == ''.

• Odd number of lines:

  A
  B
  C
  

It will result in line1 == 'C\n' and line2 == ''.

None of them is what you want. There's no two lines there in those two variables. Your code right after this inner loop simply don't receive those lines at all.

UPDATE: Solution to find the first duplicated line in the file:

Please replace the inner while loop above with the following:

lines = set()
line = None
for line in inFile:
    if line in lines:
        break
    lines.add(line)
else:
    line = None

If line is not None after this inner loop, then it is the duplicated line. If line is None, then there are no duplicated lines in that file.

Is it what you need?

UPDATE: According to the latest "specification" the solution would be:

# Read file and compare
inFile = open(fileName)
previous_line = None
line = None
for line in inFile:
    if line == previous_line:
        break
    previous_line = line
else:
    line = None
inFile.close()
if line is not None:
    break

Does it do what you want to achieve?