inspect.stack() or inspect.currentframe() gives "list index out ofrange error"

[deluxstar]

Hi,

We have an application working on several servers generally written
with Python 2.6 and Twisted 10.
The source codes are located in one server and compiled in this
server. The compiled files are copied to other server via network and
application server works with these compiled files.

In this application, I have to write a function to return a value of
the caller object that calles this function. The function may be
called from several modules of the application. To achieve this goal,
I try to use the python inspect module:

curframe = inspect.currentframe()
calframe = inspect.getouterframes(curframe, 2)
calframe[1][0].f_locals['variable']

This sample code works on local development environment both on linux
and windows. When checked in to production environment,
inspect.currentframe() or inspect.stack() function gives "List index
out of range error".

When I googled, I found only one clue of copying pyc files:
http://forum.webfaction.com/viewtopic.php?pid=16808

Why inspect modules gives this error? OR Is there another way to get
the caller objects variable value?

Thanks in advance.

 

[Peter Otten]

We have an application working on several servers generally written
with Python 2.6 and Twisted 10.
The source codes are located in one server and compiled in this
server. The compiled files are copied to other server via network and
application server works with these compiled files.

In this application, I have to write a function to return a value of
the caller object that calles this function. The function may be
called from several modules of the application. To achieve this goal,
I try to use the python inspect module:

curframe = inspect.currentframe()
calframe = inspect.getouterframes(curframe, 2)
calframe[1][0].f_locals['variable']

This sample code works on local development environment both on linux
and windows. When checked in to production environment,
inspect.currentframe() or inspect.stack() function gives "List index
out of range error".

When I googled, I found only one clue of copying pyc files:
http://forum.webfaction.com/viewtopic.php?pid=16808

Why inspect modules gives this error? OR Is there another way to get
the caller objects variable value?

Can you provide the actual traceback? Provide a small script that reproduces
the error? Add print statements and post their output?

print inspect.currentframe

curframe = inspect.currentframe() print curframe
calframe = inspect.getouterframes(curframe, 2)

print calframe

Peter

 

[deluxstar]

We have an application working on several servers generally written
with Python 2.6 and Twisted 10.
The source codes are located in one server and compiled in this
server. The compiled files are copied to other server via network and
application server works with these compiled files.

In this application, I have to write a function to return a value of
the caller object that calles this function. The function may be
called from several modules of the application. To achieve this goal,
I try to use the python inspect module:

curframe = inspect.currentframe()
calframe = inspect.getouterframes(curframe, 2)
calframe[1][0].f_locals['variable']

This sample code works on local development environment both on linux
and windows. When checked in to production environment,
inspect.currentframe() or inspect.stack() function gives "List index
out of range error".

When I googled, I found only one clue of copying pyc files:
http://forum.webfaction.com/viewtopic.php?pid=16808

Why inspect modules gives this error? OR Is there another way to get
the caller objects variable value?

Can you provide the actual traceback? Provide a small script that reproduces
the error? Add print statements and post their output?

print inspect.currentframe> curframe = inspect.currentframe()
print curframe

calframe = inspect.getouterframes(curframe, 2)

print calframe

Peter

The traceback is:
2010-09-25 10:50:38+0300 [-] Traceback (most recent call last):
2010-09-25 10:50:38+0300 [-] File "../appsrv/lqcommon.py", line 983,
in getPRMS
2010-09-25 10:50:38+0300 [-] File "/usr/lib/python2.6/inspect.py",
line 931, in getouterframes
2010-09-25 10:50:38+0300 [-] framelist.append((frame,) +
getframeinfo(frame, context))
2010-09-25 10:50:38+0300 [-] File "/usr/lib/python2.6/inspect.py",
line 906, in getframeinfo
2010-09-25 10:50:38+0300 [-] lines, lnum = findsource(frame)
2010-09-25 10:50:38+0300 [-] File "/usr/lib/python2.6/inspect.py",
line 568, in findsource
2010-09-25 10:50:38+0300 [-] if pat.match(lines[lnum]): break
2010-09-25 10:50:38+0300 [-] IndexError: list index out of range

It is hard to reproduce the error with a script. I will work and send
if I success.
If the traceback tells smth, please tell me
Thnx

 

[Steven D'Aprano]

The traceback is:
2010-09-25 10:50:38+0300 [-] Traceback (most recent call last):
2010-09-25 10:50:38+0300 [-] File "../appsrv/lqcommon.py", line 983,
in getPRMS
2010-09-25 10:50:38+0300 [-] File "/usr/lib/python2.6/inspect.py",
line 931, in getouterframes
2010-09-25 10:50:38+0300 [-] framelist.append((frame,) +
getframeinfo(frame, context))
2010-09-25 10:50:38+0300 [-] File "/usr/lib/python2.6/inspect.py",
line 906, in getframeinfo
2010-09-25 10:50:38+0300 [-] lines, lnum = findsource(frame)
2010-09-25 10:50:38+0300 [-] File "/usr/lib/python2.6/inspect.py",
line 568, in findsource
2010-09-25 10:50:38+0300 [-] if pat.match(lines[lnum]): break
2010-09-25 10:50:38+0300 [-] IndexError: list index out of range

I'm going to take a wild guess here.

My guess is that you've copied the .pyc file onto the server, BUT there
is also an *older* version of the .py file there as well. Because the
modification date is older than that of the .pyc file, Python executes
the compiled code from the .pyc file. But when you search for the source
code, the old .py file is discovered -- but it doesn't have the right
number of lines, and so you end up with an IndexError.

 

[Wolfgang Rohdewald]

My guess is that you've copied the .pyc file onto the server,
BUT there is also an older version of the .py file there as
well. Because the modification date is older than that of the
.pyc file, Python executes the compiled code from the .pyc
file.

that would be horrible - this is what our own legacy software
does. A maintenance nightmare. Think adjusting system time
or "cp -a spam.py"

Actually the docs say something different:

The modification time of the version of spam.py used to create
spam.pyc is recorded in spam.pyc, and the .pyc file is ignored if
these don’t match.

found here:
http://docs.python.org/tutorial/modules.html

 

[Terry Reedy]

The traceback is:
2010-09-25 10:50:38+0300 [-] Traceback (most recent call last):
2010-09-25 10:50:38+0300 [-] File "../appsrv/lqcommon.py", line 983,
in getPRMS
2010-09-25 10:50:38+0300 [-] File "/usr/lib/python2.6/inspect.py",
line 931, in getouterframes
2010-09-25 10:50:38+0300 [-] framelist.append((frame,) +
getframeinfo(frame, context))
2010-09-25 10:50:38+0300 [-] File "/usr/lib/python2.6/inspect.py",
line 906, in getframeinfo
2010-09-25 10:50:38+0300 [-] lines, lnum = findsource(frame)
2010-09-25 10:50:38+0300 [-] File "/usr/lib/python2.6/inspect.py",
line 568, in findsource
2010-09-25 10:50:38+0300 [-] if pat.match(lines[lnum]): break
2010-09-25 10:50:38+0300 [-] IndexError: list index out of range

It is hard to reproduce the error with a script. I will work and send
if I success.
If the traceback tells smth, please tell me

The traceback is terribly difficult to read with the timestamps added.
They are not from Python. In the future, please try to suppress them or
use a global search/replace (with nothing) before posting such.