Python – Why do I get the No such file or directory error when executing a python script?

Possible Duplicate:
ubuntu /usr/bin/env: python : No such file or directory

I’m new to Hadoop streaming. I’m having a problem learning mapreduce.
Here is my mapper.py code:

#!/usr/bin/env python 

import sys

# input comes from STDIN (standard input)
for line in sys.stdin:
    # remove leading and trailing whitespace
    line = line.strip()
    # split the line into words
    words = line.split()
    # increase counters
    for word in words:
        # write the results to STDOUT (standard output);
        # what we output here will be the input for the
        # Reduce step, i.e. the input for reducer.py
        #
        # tab-delimited; the trivial word count is 1
        print '%s\t%s' % (word, 1)

When I do the following:

hadoop@Chris-ubuntu:/home/test$ echo "I love China I love ieee I love python" | /home/test/mapper.py 

I got the result :

: No such file or directory

However, I’m sure the file does exist in that path and can be seen via ls. So I’m just wondering how to fix this.