Why can't I call read() twice on an open file?

Question

For an exercise I'm doing, I'm trying to read the contents of a given file twice using the read() method. Strangely, when I call it the second time, it doesn't seem to return the file content as a string?

Here's the code

f = f.open()

# get the year
match = re.search(r'Popularity in (\d+)', f.read())

if match:
  print match.group(1)

# get all the names
matches = re.findall(r'<td>(\d+)</td><td>(\w+)</td><td>(\w+)</td>', f.read())

if matches:
  # matches is always None

Of course I know that this is not the most efficient or best way, this is not the point here. The point is, why can't I call read() twice? Do I have to reset the file handle? Or close / reopen the file in order to do that?

Answer 1

I always find the read method something of a walk down a dark alley. You go down a bit and stop but if you are not counting your steps you are not sure how far along you are. Seek gives the solution by repositioning, the other option is Tell which returns the position along the file. May be the Python file api can combine read and seek into a read_from(position,bytes) to make it simpler - till that happens you should read this page.