What is wrong with my little 20-line program?

[Alan Stewart]

temps.txt

# TEMPERATURE CONVERSIONS / temps.txt / 09/01/2011
# CELSIUS / FAHRENHEIT / CONVERSIONS       
# Alan Stewart  /  1-(361)-980-1877
#                                                
#!/usr/local/bin/python
import string, sys
# if no arguments were given,print a helpful message.
if len (sys.argv) == 1:
    print'Usage: celsius temp1 temp2  ...'           
    sys.exit(0)                
# Loop over the arguments              
for i in sys.argv[1:]:
    try:        
        fahrenheit=float(string.ato1(i))
    except string.atoi_error:
        print repr(i), "Not a numeric value."
    else:
        celsius=(fahrenheit-32)*5.0/9.0
        print '%iF=%iC' %(int(fahrenheit),int(celsius+0.5))

[bvdet]

You misspelled string.atoi

[Dev Player]

Try it like this:

#!/usr/local/bin/python

# TEMPERATURE CONVERSIONS / temps.txt / 09/01/2011
# CELSIUS / FAHRENHEIT / CONVERSIONS
# Alan Stewart  /  1-(361)-980-1877
#              

import sys

# If no arguments were given,print a helpful message.
if len(sys.argv) <= 1:
    print('Usage: celsius temp1 temp2  ...')
    sys.exit(0)             

# Loop over the arguments
for i in sys.argv[1:]:
    try:
        fahrenheit=float(i)
    except ValueError:
        print('%s is not a numeric value.' % repr(i))
    else:
        celsius=(fahrenheit-32)*5.0/9.0
        print('%iF=%iC' % (int(fahrenheit), int(celsius+0.5)))

I removed the space between len and (sys.argv), changed print to Python 3.0 format, removed import string as float('1.0') or float('5') converts to a float and a ValueError is raised when float('a') or some such thing is entered. also moved the #!/usr/local/bin/python
comment to line 0 (line1) as unix looks for that line there.

I noticed you do a sys.exit(0) if the app doesn't receive the right commandline parameters. However this is typically the return value if the program ran 100% correctly. You may want to do a sys.exit(1) there. And for consistancey sake do a sys.exit(0) at the bottom of the temps.py