Python 初体验（八）

编写简单脚本：

you draw n random uniformly distributed numbers, where n is given on the command line, and compute the average of these numbers.

the lesson learned from this little prctice can be concluded as:

1. generation of random number
2. read parameter from command line with sys.argv
3. application of regular expression in Python

import sys
import random
import re
if len(sys.argv) != 2:
    print 'invalid parameter input'
    sys.exit()
pattern = re.compile(r'^\d+$')
match = pattern.match(sys.argv[1])
if match:
    b=[]
    a = int(sys.argv[1])
    while(a != 0):
        b.append(random.uniform(-1,1))
        print '%.4f' % b[-1]
        a -= 1
    average = sum(b)/len(b)
    print 'Average: %.4f' % average
else:
    print 'invalid parameter input'
    sys.exit()