通过检测和异常处理记录信用卡交易记录
打开一个信用卡交易的数据文件（carddata.txt）,加载所有交易，包括解释的字符串。
加载数据如下：
previous balance
25
debits
21.64
541.24
25
credits
-25
-541.24
finance charge/late fees
7.30
5读取信用卡的数据文件，并计算最终的余额。
同时还有一个处理过程的日志文件生成。
主要使用try-except语句检测异常。
代码如下：
# -*- coding: utf-8 -*-
"""
Created on Mon Aug 21 17:13:14 2017
@author: zhang
"""
#!/usr/bin/env python
def safe_float(object):
try:
retval = float(object)
except (ValueError, TypeError), diag:
retval = str(diag)
return retval
def main():
"""handle all the data processing"""
log = open('cardlog.txt', 'w')
try:
ccfile = open('carddata.txt','r')
except IOError, e:
log.write('no transactions in this month')
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):
total += result
log.write('current value:%.2f data...processed\n' % total)
else:
log.write('ignored: %s' % result)
print '$%.2f (new balance)' % total
log.close()
if __name__=='__main__':
main()运行的结果如下：
$58.94 (new balance)日志文件如下：
account log:
ignored: could not convert string to float: previous balance
current value:25.00 data...processed
ignored: could not convert string to float: debits
current value:46.64 data...processed
current value:587.88 data...processed
current value:612.88 data...processed
ignored: could not convert string to float: credits
current value:587.88 data...processed
current value:46.64 data...processed
ignored: could not convert string to float: finance charge/late fees
current value:53.94 data...processed
current value:58.94 data...processed