String Formatting

[felix001]

Ive written a small program to convert celcuis o Fahrenheit and vice versa.
The script as it stands works :

#!/usr/bin/python

import sys

def convert(t,fc):
        if t == "c":
                print (fc * 9) / 5 + 32,"Degress Fahrenheit"
        elif t == "f":
                print (fc - 32) / 9 * 5,"Degress Celcuis"

if len(sys.argv) < 3:
        print 'Insufficient Parameters.'
        sys.exit()
if sys.argv[1].startswith('--'):
        option = sys.argv[1][2:]
        # fetch sys.argv[1] but without the first two characters
        if option == 'version':
                print 'Version 0.1'
        elif option == 'help':
                print '''\
This program coverts the temperatures celcius and farenheit.
Options include:
  --version   : Prints the version number
  --help      : Display this help'''
        else:
                print 'Unknown option.'
        sys.exit()
else:
        type = sys.argv[1]
        temp = int(sys.argv[2])
        convert(type,temp)

But if instead of using the int(sys.argv[2]) to convert the string to an intergar, I use string formatting such as .. (shown below) i get the error :

TypeError: unsupported operand type(s) for %: 'int' and 'str'

def convert(t,fc):
        if t == "c":
                print ("%d" * 9) / 5 + 32,"Degress Fahrenheit" % (fc)
        elif t == "f":
                print ("%d" - 32) / 9 * 5,"Degress Celcuis" % (fc)

Shouldn't the string format convert the fc to a decimal int ?

Thanks,

[Gribouillis]

It would be better to compute with floating numbers to avoid division issues (like 5/9 == 0)

def nearest_int(number):
    return int(number + (0.5 if number >= 0 else -0.5))

print "%d Degrees Farenheit" % nearest_int(float(fc) * 9 / 5 + 32)

Also it would be much better to use the optparse or argparse module to handle command line arguments and options. Read this tutorial http://www.alexonlinux.com/pythons-optparse-for-human-beings