jupyter notebook：使用argparse包存在的问题及解决

Posted 2022-11-06 qq_784583650

argparse模块

argparse是python用于解析命令行参数和选项的标准模块

导入argparse包

import argparse

遇到的问题

parser = argparse.ArgumentParser()
parser.parse_args()

usage: __main__.py [-h]
__main__.py: error: unrecognized arguments: -f /run/user/1006/jupyter/kernel-ce6cfb61-acb9-40bf-a59b-ff6e1c1eacae.json



An exception has occurred, use %tb to see the full traceback.


SystemExit: 2

问题分析

由于在jupyter notebook中，args不为空，可以查看系统环境变量，大概是下面形式

import sys
sys.argv

['/home/liu/anaconda2/lib/python2.7/site-packages/ipykernel/__main__.py',
 '-f',
 '/run/user/1006/jupyter/kernel-ce6cfb61-acb9-40bf-a59b-ff6e1c1eacae.json']

可以看出，错误中的-f /…来自这里，可以查看parse_args()函数源码
以及和其调用的函数parse_known_args()源码
虽然args默认参数为None，但是实质为args = _sys.argv[1:]
所以在jupyter中，可以查看自己需要的系统环境变量，然后以list的数据形式传参给args则可以了

parser.parse_args??
parser.parse_known_args??

Signature: parser.parse_args(args=None, namespace=None)
Source:   
    def parse_args(self, args=None, namespace=None):
        args, argv = self.parse_known_args(args, namespace)
        if argv:
            msg = _('unrecognized arguments: %s')
            self.error(msg % ' '.join(argv))
        return args
File:      /home/liu/anaconda2/lib/python2.7/argparse.py
Type:      instancemethod

Signature: parser.parse_known_args(args=None, namespace=None)
Source:   
    def parse_known_args(self, args=None, namespace=None):
        if args is None:
            # args default to the system args
            args = _sys.argv[1:]
        else:
            # make sure that args are mutable
            args = list(args)

        # default Namespace built from parser defaults
        if namespace is None:
            namespace = Namespace()

        # add any action defaults that aren't present
        for action in self._actions:
            if action.dest is not SUPPRESS:
                if not hasattr(namespace, action.dest):
                    if action.default is not SUPPRESS:
                        setattr(namespace, action.dest, action.default)

        # add any parser defaults that aren't present
        for dest in self._defaults:
            if not hasattr(namespace, dest):
                setattr(namespace, dest, self._defaults[dest])

        # parse the arguments and exit if there are any errors
        try:
            namespace, args = self._parse_known_args(args, namespace)
            if hasattr(namespace, _UNRECOGNIZED_ARGS_ATTR):
                args.extend(getattr(namespace, _UNRECOGNIZED_ARGS_ATTR))
                delattr(namespace, _UNRECOGNIZED_ARGS_ATTR)
            return namespace, args
        except ArgumentError:
            err = _sys.exc_info()[1]
            self.error(str(err))
File:      /home/liu/anaconda2/lib/python2.7/argparse.py
Type:      instancemethod

问题解决

parser = argparse.ArgumentParser()
parser.add_argument("--verbosity", help="increase output verbosity")
args = parser.parse_args(args=[])
print(args)

Namespace(verbosity=None)

argparse参考文档

参考文档