DevFailed does not support indexing

# 6 years ago
AlexS	Hello. It seems that python3 version of PyTango 9.2.2 does not support indexing of DevFailed. I tried the following code on python 2 and python3. `import tango ex = None try: dev = tango.DeviceProxy('a/b/c') # This device does not exist except tango.DevFailed as e: ex = e ex.args[0]# Works well ex[0] # Fails on python3 with TypeError: 'DevFailed' object does not support indexing` Info: Ubuntu 18.04 PyTango 9.2.2 python 3.6 libboost-python1.65

# 6 years ago

Hello.
It seems that python3 version of PyTango 9.2.2 does not support indexing of DevFailed.
I tried the following code on python 2 and python3.


import tango
ex = None
try:
        dev = tango.DeviceProxy('a/b/c') # This device does not exist
except tango.DevFailed as e:
        ex = e
ex.args[0]# Works well
ex[0] # Fails on python3 with TypeError: 'DevFailed' object does not support indexing

Info:
Ubuntu 18.04
PyTango 9.2.2
python 3.6
libboost-python1.65

# 6 years ago
Andy	I am not a PyTango expert but it seems like the DevFailed type has changed and you now need to specify ex.args[0] e.g. `In [37]: print(ex.args[0]) DevError[ desc = device a/b/c not defined in the database ! origin = DataBase::ImportDevice() reason = DB_DeviceNotDefined severity = ERR]` Maybe a Python expert can explain the new type. Andy

# 6 years ago
AlexS	I mean that the same code works well on python 2 but fails on python 3. `import tango ex = None try: dev = tango.DeviceProxy('a/b/c') # This device does not exist except tango.DevFailed as e: ex = e ex.args[0]# Works well on both python2 python3 ex[0] # Works on python2 but fails on python3 with TypeError: 'DevFailed' object does not support indexing` Packages: python3-pytango: 9.2.2-1build1 python-pytango: 9.2.2-1build1

# 6 years ago

AlexS

I mean that the same code works well on python 2 but fails on python 3.


import tango
ex = None
try:
        dev = tango.DeviceProxy('a/b/c') # This device does not exist
except tango.DevFailed as e:
        ex = e
ex.args[0]# Works well on both python2 python3
ex[0] # Works on python2 but fails on python3 with TypeError: 'DevFailed' object does not support indexing

Packages:
python3-pytango: 9.2.2-1build1
python-pytango: 9.2.2-1build1

# 6 years ago
Vincent M	Yes, BaseException.__getitem__ has been removed in python 3. Do you think it's a problem?

# 6 years ago
AlexS	I missed that Exception API was changed. It is not a huge problem. In my opinion, there is no need to provide full compatibility with old code. Yes, Some problems could arise during porting python2 code to python3. I think that the optimal solution is to create "Porting guideline" page in Docs. Edited 6 years ago

# 6 years ago
Laurent	Hi, related to this issue, we did find a bug in pyutil.py in method __Util__create_device: try: db.import_device(device_name) except DevFailed as df: device_exists = not df[0].reason == "DB_DeviceNotDefined" it should be: try: db.import_device(device_name) except DevFailed as df: device_exists = not df.args[0].reason == "DB_DeviceNotDefined" Could we get a fix in the next release, please? Thanks for you help. Laurent Laurent

# 6 years ago

Laurent

Hi,
related to this issue, we did find a bug in pyutil.py in method __Util__create_device:
try:
db.import_device(device_name)
except DevFailed as df:
device_exists = not df[0].reason == "DB_DeviceNotDefined"

it should be:
try:
db.import_device(device_name)
except DevFailed as df:
device_exists = not df.args[0].reason == "DB_DeviceNotDefined"

Could we get a fix in the next release, please?

Thanks for you help.

Laurent

Laurent