Python: read all text file lines in loop

Just iterate over each line in the file. Python automatically checks for the End of file and closes the file for you (using the with syntax).

with open('fileName', 'r') as f:
    for line in f:
       if 'str' in line:
           break

There are situations where you can't use the (quite convincing) with... for... structure. In that case, do the following:

line = self.fo.readline()
if len(line) != 0:
     if 'str' in line:
         break

This will work because the the readline() leaves a trailing newline character, where as EOF is just an empty string.

There's no need to check for EOF in python, simply do:

with open('t.ini') as f:
   for line in f:
       # For Python3, use print(line)
       print line
       if 'str' in line:
          break

Why the with statement:

It is good practice to use the with keyword when dealing with file objects. This has the advantage that the file is properly closed after its suite finishes, even if an exception is raised on the way.