Suppose that we have a list and we need to apply some function on each element of it.
One good example is getting a file content using readlines(). This function will get every line, including the newline (e.g. \n.)
One thing we can do is this:
r =  for line in fh.readlines(): r.append(line.strip())
But a better way is to use map and a lambda function:
map((lambda(x): x.strip()), self.fh.readlines())