在使用-h时,python argparse崩溃了

Question

当我运行./foo.py -h,其中foo.py是以下代码时,它会因错误而崩溃

ValueError:要解压缩的值太多

这是代码.

#!/usr/bin/python
import argparse

parser = argparse.ArgumentParser(description='Find matrices.')
parser.add_argument('integers', metavar=('n','h'), type=int, nargs=2, help='Dimensions of the matrix')
(n,h)= parser.parse_args().integers

我的代码中有错误吗？

完整的追溯(Python 2.7.3):

Traceback (most recent call last):
  File "argp.py", line 15, in <module>
    (n,h)= parser.parse_args().integers
  File "/usr/lib/python2.7/argparse.py", line 1688, in parse_args
    args, argv = self.parse_known_args(args, namespace)
  File "/usr/lib/python2.7/argparse.py", line 1720, in parse_known_args
    namespace, args = self._parse_known_args(args, namespace)
  File "/usr/lib/python2.7/argparse.py", line 1926, in _parse_known_args
    start_index = consume_optional(start_index)
  File "/usr/lib/python2.7/argparse.py", line 1866, in consume_optional
    take_action(action, args, option_string)
  File "/usr/lib/python2.7/argparse.py", line 1794, in take_action
    action(self, namespace, argument_values, option_string)
  File "/usr/lib/python2.7/argparse.py", line 994, in __call__
    parser.print_help()
  File "/usr/lib/python2.7/argparse.py", line 2313, in print_help
    self._print_message(self.format_help(), file)
  File "/usr/lib/python2.7/argparse.py", line 2280, in format_help
    formatter.add_arguments(action_group._group_actions)
  File "/usr/lib/python2.7/argparse.py", line 273, in add_arguments
    self.add_argument(action)
  File "/usr/lib/python2.7/argparse.py", line 258, in add_argument
    invocations = [get_invocation(action)]
  File "/usr/lib/python2.7/argparse.py", line 534, in _format_action_invocation
    metavar, = self._metavar_formatter(action, action.dest)(1)
ValueError: too many values to unpack

Answer 1

这是一个错误,argparse其中nargs,元组metavar和位置参数不混合.integers是位置参数,而不是可选--integers开关.

要么使它成为可选参数:

parser.add_argument('--integers', metavar=('n','h'), type=int, nargs=2, help='Dimensions of the matrix')

或使用两个位置参数:

parser.add_argument('n', type=int, help='Dimensions of the matrix')
parser.add_argument('h', type=int, help='Dimensions of the matrix')

代替.

请参阅Python错误跟踪器中的问题14074以获取针对该错误的建议修复.