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我正在使用“Learn Python the Hard Way”并使用 PyScripter 编写和运行我的代码。

在练习 13 中，我必须运行以下代码：

from sys import argv


script, first, second, third = argv

print "The script is called:", script
print "Your first variable is:", first
print "Your second variable is:", second
print "Your third variable is:", third

当我运行它时，我收到一条错误消息

ValueError: need more than 1 value to unpack

我已阅读有关同一主题的其他问题，但似乎找不到有效的答案。

我对编码也很陌生，所以解释如何去做会很棒！

4

1 回答 1

0

您的脚本只有在您将三个命令行参数传递给它时才能工作。例如：

script.py 1 2 3

您不能使用任何其他数量的命令行参数，否则ValueError将引发 a。

也许您应该通过检查收到的参数数量然后适当地分配名称first、、second和来使您的脚本更健壮一些。third

下面是一个演示：

from sys import argv, exit

argc = len(argv)  # Get the number of commandline arguments

if argc == 4:
    # There were 3 commandline arguments
    script, first, second, third = argv
elif argc == 3:
    # There were only 2 commandline arguments
    script, first, second = argv
    third = '3rd'
elif argc == 2:
    # There was only 1 commandline argument
    script, first = argv
    second = '2nd'
    third = '3rd'
elif argc == 1:
    # There was no commandline arguments
    script = argv[0]
    first = '1st'
    second = '2nd'
    third = '3rd'
else:
    print "Too many commandline arguments"
    exit(1)

print "The script is called:", script
print "Your first variable is:", first
print "Your second variable is:", second
print "Your third variable is:", third

当然，这只是一个例子。您可以在 if 语句中做任何您想做的事情（将名称分配给不同的名称、引发异常、打印消息、退出脚本等）。这里重要的部分是argc = len(argv)检查脚本接收到多少参数的行和 if 语句。

于 2014-12-07T20:59:27.687 回答