Issue in parsing the string output from the command using "subprocess"

[srinivasan]

Dear Python Experts Team,

As am newbie to python and learning python, working on embedded linux
platform, my intention is to delete all the SSID's before connecting my
Wi-Fi module to specific SSID., I am trying to parse command output using
the "subprocess"  with wrapper "execute_cmd_output_string" written on
it described
as below,  using the nmcli commands "*nmcli -t -f TYPE,UUID con" and "**"nmcli
connection delete uuid ".*

Could you please help me, what could be the bug in the below method "*def
wifi_disconnect_reconnect(self, ssid, pw):"  *using the method
"execute_cmd_output_string" (in-turn uses "subprocess") which is failing to
give correct output of., UUID's  for *"nmcli connection delete uuid "*  ?

But which works fine with "commands.getstatusoutput" (res =
commands.getstatusoutput("nmcli -t -f TYPE,UUID con")), but I dont want to
include "commands.getstatusoutput" which costs me for including one more
python module in my rootfs

Typical output for "nmcli -t -f TYPE,UUID con"

~$ nmcli -t -f TYPE,UUID con
802-11-wireless:3f5011d4-5681-4fed-8dea-95dee790e9e2
802-11-wireless:bfb93be0-740d-426e-b215-0fdc2f652877
802-11-wireless:69b60cf4-65aa-442b-a54c-fb82905adb0d
802-11-wireless:dc2a15ec-d3da-491e-9c8f-cb054f375837
802-11-wireless:5164e7f2-4489-462e-b093-76bc51bf1303
802-11-wireless:d462e8c4-fac7-42f2-8f9a-6846f52d4e8c
802-11-wireless:e5020744-5c9c-453c-92ec-7a854fc893e6
802-11-wireless:eed3358e-8635-471d-b7e9-5c2973a05128
802-11-wireless:ceea6707-a929-4941-9047-a75e061914b6
802-11-wireless:dd6b9c83-db7b-42b9-99c0-14a04f6f35f5
802-11-wireless:9f764fff-6288-49c4-9412-902e89230136
802-11-wireless:72c627cd-77a3-4d16-bb2c-058040d8e4fc
~$

*Python Code Snipeet:*
*------------------------------*
*    def wifi_disconnect_reconnect(self, ssid, pw):*
*        """*
*            Connect to Access point using SSID and PW.*

*            :param ssid: SSID of the ACCESS POINT.*
*            :param pw: password for connecting to the access point.*
*            :return: command output as True or False.*
*        """*

*        cmd = "nmcli -t -f TYPE,UUID con"*
*        res = self._helper.execute_cmd_output_string(cmd)*
*        print(res)*
*        lines = res[1].split('\n') ------------------------> I suspect the
issue might be here*
*        print(lines)*

*        for line in lines:*
*            parts = line.split(":")*
*            print(parts)*
*            print(parts[1])*
*            if (parts[0] == "802-11-wireless"):*
*                print("nmcli connection delete uuid "+ parts[1])*
*                os.system("nmcli connection delete uuid "+ parts[1])*

*        cmd = "nmcli device wifi connect '%s' password %s" % (ssid, pw)*
*        exit_code = self._helper.execute_cmd_return_code(cmd)*

*        return True if exit_code == 0 else False*


    def execute_cmd_output_string(self, cmd, enable_shell=False):
        """
            Execute a command and return its output as a string.

            :param cmd: abs path of the command with arguments
            :param enable_shell : force the cmd to be run as shell script
            :return: a string.
        """

        try:
            result = subprocess.check_output(split(cmd),
                                             stderr=subprocess.STDOUT,
                                             shell=enable_shell)

        except subprocess.CalledProcessError as e:
            s = """While executing '{}' something went wrong.
                Return code == '{}'
                Return output:\n'{}'
                """.format(cmd, e.returncode, e.output, shell=enable_shell)
            raise AssertionError(s)

        return result.strip().decode("utf-8")


if __name__ == "__main__":
    m = wifi()
    print("disconnect and reconnect")
    print(m.wifi_disconnect_reconnect("NaWiFi", "abcds"))


*Errors:*
-----------
Traceback (most recent call last):
802-11-wireless:3f5011d4-5681-4fed-8dea-95dee790e9e2
802-11-wireless:dc2a15ec-d3da-491e-9c8f-cb054f375837
802-11-wireless:5164e7f2-4489-462e-b093-76bc51bf1303
  File
"/home/srinivasan/Downloads/qa_wifi_nov15_after_incorporating_thilo_comments_zip/qa/test_library/wifi.py",
line 153, in <module>
802-11-wireless:d462e8c4-fac7-42f2-8f9a-6846f52d4e8c
    print(m.wifi_connect("NI WiFi", "T.f.o.s.1996!"))
802-11-wireless:e5020744-5c9c-453c-92ec-7a854fc893e6
802-11-wireless:eed3358e-8635-471d-b7e9-5c2973a05128
  File
"/home/srinivasan/Downloads/qa_wifi_nov15_after_incorporating_thilo_comments_zip/qa/test_library/wifi.py",
line 77, in wifi_connect
802-11-wireless:ceea6707-a929-4941-9047-a75e061914b6
    print(parts[1])
802-11-wireless:dd6b9c83-db7b-42b9-99c0-14a04f6f35f5
*IndexError: list index out of range*
802-11-wireless:9f764fff-6288-49c4-9412-902e89230136
802-11-wireless:72c627cd-77a3-4d16-bb2c-058040d8e4fc
[u'0']
[u'0']

Process finished with exit code 1
But when I execute the below the command using the python module
"commands". I am able to successfully parse the multi line string output
and extarct the UUID's from the command "nmcli -t -f TYPE,UUID con" and
pass it to *"nmcli connection delete uuid " for* deleting all the SSID's
before connecting Wi-Fi to specific SSID.

* def wifi_disconnect_reconnect(self, ssid, pw):*
*        """*
*            Connect to Access point using SSID and PW.*

*            :param ssid: SSID of the ACCESS POINT.*
*            :param pw: password for connecting to the access point.*
*            :return: command output as True or False.*
*        """*
*        res = commands.getstatusoutput("nmcli -t -f TYPE,UUID con")*
*        lines = res[1].split('\n')*

*        for line in lines:*
*            parts = line.split(":")*
*            if (parts[0] == "802-11-wireless"):*
*                os.system("nmcli connection delete uuid "+ parts[1])*
Kindly do the needful, as I am wandering for any clues what's going wrong
with error and the highlighted code snippet...

Many Thanks in advance