Python argparse:默认参数存储为字符串，而不是列表 [英] Python argparse: default argument stored as string, not list

问题描述

我无法从文档中找出 argparse 的这种行为:

I cannot figure out this behaviour of argparse from the documentation:

import argparse

parser.add_argument("--host", metavar="", dest="host", nargs=1, default="localhost", help="Name of host for database.  Default is 'localhost'.")
args = parser.parse_args()
print(args)

这是带有和不带有--host"参数的输出:

Here is the output with and without an argument for "--host":

>> python demo.py
Namespace(host='localhost')

>> python demo.py --host host
Namespace(host=['host'])

特别是:为什么--host"的参数在指定时存储在列表中，而在使用默认值时不存储?

In particular: why does the argument to "--host" get stored in a list when it is specified but not when the default is used?

推荐答案

删除nargs"关键字参数.一旦定义了该参数，argparse 就会假设您的参数是一个列表(nargs=1 表示具有 1 个元素的列表)

Remove the "nargs" keyword argument. Once that argument is defined argparse assumes your argument is a list (nargs=1 meaning a list with 1 element)

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