codecs_open_write_IndexError_out_of_range.py

#1/usr/bin/env python

# this is from The Python
# Standard Library by example
# ISBN13: 9780321767349


from codecs_to_hex import to_hex

import codecs
import sys

encoding = sys.argv[1]
filename = encoding + '.txt'

print 'Writing to', filename
with codecs.open(filename, mode='wt', encoding=encoding) as f:
    f.write(u'pi: \u03c0')

# Determine the byte grouping to use for to_hex()
nbytes = {'utf-8': 1,
          'utf-16': 2,
          'utf-32': 4,
          }.get(encoding, 1)

# Show the raw bytes in the file
print 'File contents:'
with open(filename, mode='rt') as f:
    print to_hex(f.read(), nbytes)

""" Traceback (most recent call last):
    File "codecs_open_write.py", line 13, in <module>
    encoding = sys.argv[1]
    IndexError: list index out of range
"""