信用卡交易系统 Python

#!/usr/bin/env python
#--*-- coding:utf-8 --*--

#safe_float 的函数主体
def safe_float(obj):
'safe version of float()'
try:
retval = float(obj)
except (ValueError,TypeError),diag:
retval = str(diag)
return retval

def main():
'handles all the data processing'
log = open('cardlog.txt','w') #记录log
try:
ccfile = open('carddata.txt','r')
except IOError,e:
log.write('no txns this month\n')
log.close()
return

txns = ccfile.readlines()
ccfile.close()
total = 0.00
log.write('account log:\n')

for eachTxn in txns:
result = safe_float(eachTxn)
if isinstance(result,float): #检查是否为float
total += result
log.write('data... processed\n')#写入
else:
log.write('ignore:%s'%result)
print '$%s.2f (new balance)'%(total)
log.close()

if __name__ == '__main__':
main()