python on ubuntu linux : json.decoder.JSONDecodeError: Expecting value: line 2 column 6

Question

我在运行 python 脚本 Ubuntu 16.04.

上遇到错误

当我运行相同的代码但不确定哪个包未正确安装时，它在 Windows 上工作正常。

import subprocess
import json

#one vnet and one subnet in the resourcegroup.
def get_vnet_name(resourcegroup):
    get_vnet_command=["az","network","vnet","list","--resource-group",resourcegroup]
    get_vnet=subprocess.run(get_vnet_command, shell = True, stdout=subprocess.PIPE, stderr = subprocess.PIPE)
    a=get_vnet.stdout.decode('utf-8')
    d=json.loads(a)
    for item in d:
        vname=item["name"]
        subnets=item["subnets"]
    for i in subnets:
        subnetname=i["name"]
    return vname,subnetname

def create_vm(vm_resourcegroup,vm_name, vm_image,vm_username, vm_passowrd,vm_vnet,vm_subnet, vm_size):
    create_vm_command=["az","vm","create","--resource-group",vm_resourcegroup,"--name",vm_name,"--image",vm_image, "--admin-username", vm_username,"--admin-password",vm_passowrd,"--vnet-name",vm_vnet,"--subnet",vm_subnet,"--size", vm_size]
    create_vm=subprocess.run(create_vm_command, shell = True, stdout=subprocess.PIPE, stderr = subprocess.PIPE)
    return


if __name__=="__main__":
    rscgroup_name="vm-test-group"
    avm_name="testvm1"
    avm_image="Win2019Datacenter"
    avm_username="myuser"
    avm_password="mypassword"
    avm_size="Standard_D2_V3"
    vault_name = "aqrahkeyvault"
    certificate_name = "staticwebsite"

    avm_vnet,avm_subnet=get_vnet_name(rscgroup_name)
    create_vm(rscgroup_name,avm_name,avm_image,avm_username,avm_password,avm_vnet,avm_subnet,avm_size)

下面是我遇到的与 json.decoder 相关的错误：

  root@linuxvm:/home/azureuser# python3.6  test2.py
    Traceback (most recent call last):
      File "test2.py", line 32, in <module>
        avm_vnet,avm_subnet=get_vnet_name(rscgroup_name)
      File "test2.py", line 9, in get_vnet_name
        d=json.loads(a)
      File "/usr/lib/python3.6/json/__init__.py", line 354, in loads
        return _default_decoder.decode(s)
      File "/usr/lib/python3.6/json/decoder.py", line 339, in decode
        obj, end = self.raw_decode(s, idx=_w(s, 0).end())
      File "/usr/lib/python3.6/json/decoder.py", line 357, in raw_decode
        raise JSONDecodeError("Expecting value", s, err.value) from None
    json.decoder.JSONDecodeError: Expecting value: line 2 column 6 (char 6)

我已尝试安装 python，但未能解决问题。

Answer 1

我尝试重现了您的问题，并成功找到了原因。实际上，您的脚本基本上是正确的，但是您可能不会考虑 az 命令不是 return 任何结果到 stdout.

的情况

比如我的订阅里有non-existing个资源组，比如non-exist-rg。如果我将它作为参数--resource-group的值传递，下面的脚本会将return错误信息传递给stderr，stdout值为b''.

import subprocess
resourcegroup = 'non-exist-rg'
get_vnet_command=["az","network","vnet","list","--resource-group",resourcegroup]
get_vnet=subprocess.run(get_vnet_command, shell = True, stdout=subprocess.PIPE, stderr = subprocess.PIPE)

stdout & stderr 的结果如下。

>>> get_vnet.stdout
b''
>>> get_vnet.stderr
b"ERROR: Resource group 'non-exist-rg' could not be found.\r\n"

因此，如果您将 stdout 值传递给 json.loads 函数，它会抛出与您的 json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0) 相同的问题，因为 json.loads 无法处理空内容.在这里，对于 stdout 或 stderr 的 bytes 值的 decode 函数对于可以接收 bytes 值的 json.loads 不是必需的下图

所以要修复它，解决方法是检查 stdout 值是否为空或 stderr 值是否不为空。

def get_vnet_name(resourcegroup):
    get_vnet_command=["az","network","vnet","list","--resource-group",resourcegroup]
    get_vnet=subprocess.run(get_vnet_command, shell = True, stdout=subprocess.PIPE, stderr = subprocess.PIPE)
    # decode for stdout is not necessary
    # a=get_vnet.stdout.decode('utf-8')
    vname,subnetname = '', ''
    if get_vnet.stdout == b'':
        d=json.loads(get_vnet.stdout)
        for item in d:
            vname=item["name"]
            subnets=item["subnets"]
        for i in subnets:
            subnetname=i["name"]
    return vname,subnetname

然后，您需要在调用 create_vm 方法之前检查 vname 和 subnetname 值。

希望对您有所帮助。

python on ubuntu linux : json.decoder.JSONDecodeError: Expecting value: line 2 column 6

python on ubuntu linux : json.decoder.JSONDecodeError: Expecting value: line 2 column 6

python

azure

python-3.x

ubuntu-16.04

azure-cli2