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


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