help with class

[tekion]

Hello,
I am playing with class.  Below is the code snippet:
#!/usr/bin/python
      2
      3 class test_class:
      4    #import gzip
      5    def __init__(self,file):
      6       self.file = file
      7    def open_file(self):
      8       try:
      9          print "file: %s" % self.file
     10          self.xml_file = gzip.GzipFile(self.file,'r')
     11       except:
     12          print "an exception has occured"
     13       for line in self.xml_file:
     14          print "line: %s" % line
     15       self.xml_file.close()
     16
     17
     18 if __name__ == '__main__':
     19    import gzip
     20    import sys
     21    t = test_class( sys.argv[1] )
     22    t.open_file()

My question are:
1.  Why do I need to use "import gzip" on main section to get it the
script to work?  I would assume you need the import of gzip in the
class section.
2.  What is the proper way of using module in a class you are creating?