python *乘号在命令行中为什么报错，python乘号,环境Mac Os X 1

环境

Mac Os X 10.9
python 2.7

实现功能

命令行传入公式，输出结果

出错原因

‘*‘ 号把整个目录下的文件都当作参数传入了

问题

如何正确传入 * 号？

操作

输入公式 ’2 * 3‘：

python calc.py 2 * 3

print sys.argv 的结果

['calc.py', '2', 当前目录下所有文件名如't1_1.py', '3']

返回错误

Traceback (most recent call last):  File "calc.py", line 54, in <module>    main(sys.argv)  File "calc.py", line 51, in main    calc(argv)  File "calc.py", line 16, in calc    bNum = float(bNum)ValueError: could not convert string to float: backup_ver2.py

源码

#!/usr/bin/env python# -*- coding: utf-8 -*-import sysimport osdef calc(argv):    aNum = argv[1]    Opr  = argv[2]    bNum = argv[3]    if '.' in aNum:        aNum = float(aNum)    else:        aNum = int(aNum)    if '.' in bNum:        bNum = float(bNum)    else:        bNum = int(bNum)    Opr = str(Opr)    if Opr == '+': res = aNum + bNum    elif Opr == '-': res = aNum - bNum    elif Opr == '*': res = aNum * bNum    elif Opr == '/': res = aNum / bNum    elif Opr == '%': res = aNum % bNum    elif Opr == '**' or Opr == '^':        res = aNum ** bNum    else:        print "Operator error: '%s'" % Opr    o2f(argv, res)    print resdef showres():    filename = open('calc', 'r')    fileread = filename.readlines()    for eachLine in fileread:        print eachLine,    filename.close()def o2f(argv, res):    filename = open('calc', 'a')    filename.write(argv[1] + argv[2] + argv[3] + '=' + str(res) + os.linesep)    filename.close()def main(argv):    '''useage:    print -- show all the result    example: 1 + 1 -- to get the result'''    if argv[1] == 'print':        showres()    else:        calc(argv)if __name__ == '__main__':    main(sys.argv)

python calc.py 2 "*" 3

python calc.py 2 x 3

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